<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en_US" lang="en_US">
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8" />
<title>LinkedTransferQueue xref</title>
<link type="text/css" rel="stylesheet" href="../../../../../stylesheet.css" />
</head>
<body>
<div id="overview"><a href="../../../../../../api/org/jboss/netty/util/internal/LinkedTransferQueue.html">View Javadoc</a></div><pre>

<a class="jxr_linenumber" name="1" href="#1">1</a>   <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="2" href="#2">2</a>   <em class="jxr_comment"> * Copyright 2009 Red Hat, Inc.</em>
<a class="jxr_linenumber" name="3" href="#3">3</a>   <em class="jxr_comment"> *</em>
<a class="jxr_linenumber" name="4" href="#4">4</a>   <em class="jxr_comment"> * Red Hat licenses this file to you under the Apache License, version 2.0</em>
<a class="jxr_linenumber" name="5" href="#5">5</a>   <em class="jxr_comment"> * (the "License"); you may not use this file except in compliance with the</em>
<a class="jxr_linenumber" name="6" href="#6">6</a>   <em class="jxr_comment"> * License.  You may obtain a copy of the License at:</em>
<a class="jxr_linenumber" name="7" href="#7">7</a>   <em class="jxr_comment"> *</em>
<a class="jxr_linenumber" name="8" href="#8">8</a>   <em class="jxr_comment"> *    <a href="http://www.apache.org/licenses/LICENSE-2.0" target="alexandria_uri">http://www.apache.org/licenses/LICENSE-2.0</a></em>
<a class="jxr_linenumber" name="9" href="#9">9</a>   <em class="jxr_comment"> *</em>
<a class="jxr_linenumber" name="10" href="#10">10</a>  <em class="jxr_comment"> * Unless required by applicable law or agreed to in writing, software</em>
<a class="jxr_linenumber" name="11" href="#11">11</a>  <em class="jxr_comment"> * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT</em>
<a class="jxr_linenumber" name="12" href="#12">12</a>  <em class="jxr_comment"> * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the</em>
<a class="jxr_linenumber" name="13" href="#13">13</a>  <em class="jxr_comment"> * License for the specific language governing permissions and limitations</em>
<a class="jxr_linenumber" name="14" href="#14">14</a>  <em class="jxr_comment"> * under the License.</em>
<a class="jxr_linenumber" name="15" href="#15">15</a>  <em class="jxr_comment"> */</em>
<a class="jxr_linenumber" name="16" href="#16">16</a>  
<a class="jxr_linenumber" name="17" href="#17">17</a>  <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="18" href="#18">18</a>  <em class="jxr_comment"> * Written by Doug Lea with assistance from members of JCP JSR-166</em>
<a class="jxr_linenumber" name="19" href="#19">19</a>  <em class="jxr_comment"> * Expert Group and released to the public domain, as explained at</em>
<a class="jxr_linenumber" name="20" href="#20">20</a>  <em class="jxr_comment"> * <a href="http://creativecommons.org/licenses/publicdomain" target="alexandria_uri">http://creativecommons.org/licenses/publicdomain</a></em>
<a class="jxr_linenumber" name="21" href="#21">21</a>  <em class="jxr_comment"> */</em>
<a class="jxr_linenumber" name="22" href="#22">22</a>  
<a class="jxr_linenumber" name="23" href="#23">23</a>  <strong class="jxr_keyword">package</strong> org.jboss.netty.util.internal;
<a class="jxr_linenumber" name="24" href="#24">24</a>  
<a class="jxr_linenumber" name="25" href="#25">25</a>  <strong class="jxr_keyword">import</strong> java.util.AbstractQueue;
<a class="jxr_linenumber" name="26" href="#26">26</a>  <strong class="jxr_keyword">import</strong> java.util.Collection;
<a class="jxr_linenumber" name="27" href="#27">27</a>  <strong class="jxr_keyword">import</strong> java.util.ConcurrentModificationException;
<a class="jxr_linenumber" name="28" href="#28">28</a>  <strong class="jxr_keyword">import</strong> java.util.Iterator;
<a class="jxr_linenumber" name="29" href="#29">29</a>  <strong class="jxr_keyword">import</strong> java.util.NoSuchElementException;
<a class="jxr_linenumber" name="30" href="#30">30</a>  <strong class="jxr_keyword">import</strong> java.util.concurrent.BlockingQueue;
<a class="jxr_linenumber" name="31" href="#31">31</a>  <strong class="jxr_keyword">import</strong> java.util.concurrent.TimeUnit;
<a class="jxr_linenumber" name="32" href="#32">32</a>  <strong class="jxr_keyword">import</strong> java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
<a class="jxr_linenumber" name="33" href="#33">33</a>  <strong class="jxr_keyword">import</strong> java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
<a class="jxr_linenumber" name="34" href="#34">34</a>  <strong class="jxr_keyword">import</strong> java.util.concurrent.locks.LockSupport;
<a class="jxr_linenumber" name="35" href="#35">35</a>  <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="36" href="#36">36</a>  <em class="jxr_javadoccomment"> * An unbounded {@link BlockingQueue} based on linked nodes.</em>
<a class="jxr_linenumber" name="37" href="#37">37</a>  <em class="jxr_javadoccomment"> * This queue orders elements FIFO (first-in-first-out) with respect</em>
<a class="jxr_linenumber" name="38" href="#38">38</a>  <em class="jxr_javadoccomment"> * to any given producer.  The &lt;em&gt;head&lt;/em&gt; of the queue is that</em>
<a class="jxr_linenumber" name="39" href="#39">39</a>  <em class="jxr_javadoccomment"> * element that has been on the queue the longest time for some</em>
<a class="jxr_linenumber" name="40" href="#40">40</a>  <em class="jxr_javadoccomment"> * producer.  The &lt;em&gt;tail&lt;/em&gt; of the queue is that element that has</em>
<a class="jxr_linenumber" name="41" href="#41">41</a>  <em class="jxr_javadoccomment"> * been on the queue the shortest time for some producer.</em>
<a class="jxr_linenumber" name="42" href="#42">42</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="43" href="#43">43</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;Beware that, unlike in most collections, the {@code size}</em>
<a class="jxr_linenumber" name="44" href="#44">44</a>  <em class="jxr_javadoccomment"> * method is &lt;em&gt;NOT&lt;/em&gt; a constant-time operation. Because of the</em>
<a class="jxr_linenumber" name="45" href="#45">45</a>  <em class="jxr_javadoccomment"> * asynchronous nature of these queues, determining the current number</em>
<a class="jxr_linenumber" name="46" href="#46">46</a>  <em class="jxr_javadoccomment"> * of elements requires a traversal of the elements.</em>
<a class="jxr_linenumber" name="47" href="#47">47</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="48" href="#48">48</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;This class and its iterator implement all of the</em>
<a class="jxr_linenumber" name="49" href="#49">49</a>  <em class="jxr_javadoccomment"> * &lt;em&gt;optional&lt;/em&gt; methods of the {@link Collection} and {@link</em>
<a class="jxr_linenumber" name="50" href="#50">50</a>  <em class="jxr_javadoccomment"> * Iterator} interfaces.</em>
<a class="jxr_linenumber" name="51" href="#51">51</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="52" href="#52">52</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;Memory consistency effects: As with other concurrent</em>
<a class="jxr_linenumber" name="53" href="#53">53</a>  <em class="jxr_javadoccomment"> * collections, actions in a thread prior to placing an object into a</em>
<a class="jxr_linenumber" name="54" href="#54">54</a>  <em class="jxr_javadoccomment"> * {@code LinkedTransferQueue}</em>
<a class="jxr_linenumber" name="55" href="#55">55</a>  <em class="jxr_javadoccomment"> * &lt;a href="package-summary.html#MemoryVisibility"&gt;&lt;i&gt;happen-before&lt;/i&gt;&lt;/a&gt;</em>
<a class="jxr_linenumber" name="56" href="#56">56</a>  <em class="jxr_javadoccomment"> * actions subsequent to the access or removal of that element from</em>
<a class="jxr_linenumber" name="57" href="#57">57</a>  <em class="jxr_javadoccomment"> * the {@code LinkedTransferQueue} in another thread.</em>
<a class="jxr_linenumber" name="58" href="#58">58</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="59" href="#59">59</a>  <em class="jxr_javadoccomment"> * &lt;p&gt;This class is a member of the</em>
<a class="jxr_linenumber" name="60" href="#60">60</a>  <em class="jxr_javadoccomment"> * &lt;a href="{@docRoot}/../technotes/guides/collections/index.html"&gt;</em>
<a class="jxr_linenumber" name="61" href="#61">61</a>  <em class="jxr_javadoccomment"> * Java Collections Framework&lt;/a&gt;.</em>
<a class="jxr_linenumber" name="62" href="#62">62</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="63" href="#63">63</a>  <em class="jxr_javadoccomment"> * @author &lt;a href="<a href="http://www.jboss.org/netty/" target="alexandria_uri">http://www.jboss.org/netty/</a>"&gt;The Netty Project&lt;/a&gt;</em>
<a class="jxr_linenumber" name="64" href="#64">64</a>  <em class="jxr_javadoccomment"> * @author Doug Lea</em>
<a class="jxr_linenumber" name="65" href="#65">65</a>  <em class="jxr_javadoccomment"> * @author &lt;a href="<a href="http://gleamynode.net/" target="alexandria_uri">http://gleamynode.net/</a>"&gt;Trustin Lee&lt;/a&gt;</em>
<a class="jxr_linenumber" name="66" href="#66">66</a>  <em class="jxr_javadoccomment"> * @version $Rev: 2373 $, $Date: 2010-10-20 20:33:23 +0900 (Wed, 20 Oct 2010) $ (Upstream: 1.79)</em>
<a class="jxr_linenumber" name="67" href="#67">67</a>  <em class="jxr_javadoccomment"> *</em>
<a class="jxr_linenumber" name="68" href="#68">68</a>  <em class="jxr_javadoccomment"> * @param &lt;E&gt; the type of elements held in this collection</em>
<a class="jxr_linenumber" name="69" href="#69">69</a>  <em class="jxr_javadoccomment"> */</em>
<a class="jxr_linenumber" name="70" href="#70">70</a>  <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">class</strong> LinkedTransferQueue&lt;E&gt; <strong class="jxr_keyword">extends</strong> AbstractQueue&lt;E&gt;
<a class="jxr_linenumber" name="71" href="#71">71</a>      <strong class="jxr_keyword">implements</strong> BlockingQueue&lt;E&gt;, java.io.Serializable {
<a class="jxr_linenumber" name="72" href="#72">72</a>      <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">long</strong> serialVersionUID = -3223113410248163686L;
<a class="jxr_linenumber" name="73" href="#73">73</a>  
<a class="jxr_linenumber" name="74" href="#74">74</a>      <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="75" href="#75">75</a>  <em class="jxr_comment">     * *** Overview of Dual Queues with Slack ***</em>
<a class="jxr_linenumber" name="76" href="#76">76</a>  <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="77" href="#77">77</a>  <em class="jxr_comment">     * Dual Queues, introduced by Scherer and Scott</em>
<a class="jxr_linenumber" name="78" href="#78">78</a>  <em class="jxr_comment">     * (<a href="http://www.cs.rice.edu/~wns1/papers/2004-DISC-DDS.pdf)" target="alexandria_uri">http://www.cs.rice.edu/~wns1/papers/2004-DISC-DDS.pdf)</a> are</em>
<a class="jxr_linenumber" name="79" href="#79">79</a>  <em class="jxr_comment">     * (linked) queues in which nodes may represent either data or</em>
<a class="jxr_linenumber" name="80" href="#80">80</a>  <em class="jxr_comment">     * requests.  When a thread tries to enqueue a data node, but</em>
<a class="jxr_linenumber" name="81" href="#81">81</a>  <em class="jxr_comment">     * encounters a request node, it instead "matches" and removes it;</em>
<a class="jxr_linenumber" name="82" href="#82">82</a>  <em class="jxr_comment">     * and vice versa for enqueuing requests. Blocking Dual Queues</em>
<a class="jxr_linenumber" name="83" href="#83">83</a>  <em class="jxr_comment">     * arrange that threads enqueuing unmatched requests block until</em>
<a class="jxr_linenumber" name="84" href="#84">84</a>  <em class="jxr_comment">     * other threads provide the match. Dual Synchronous Queues (see</em>
<a class="jxr_linenumber" name="85" href="#85">85</a>  <em class="jxr_comment">     * Scherer, Lea, &amp; Scott</em>
<a class="jxr_linenumber" name="86" href="#86">86</a>  <em class="jxr_comment">     * <a href="http://www.cs.rochester.edu/u/scott/papers/2009_Scherer_CACM_SSQ.pdf)" target="alexandria_uri">http://www.cs.rochester.edu/u/scott/papers/2009_Scherer_CACM_SSQ.pdf)</a></em>
<a class="jxr_linenumber" name="87" href="#87">87</a>  <em class="jxr_comment">     * additionally arrange that threads enqueuing unmatched data also</em>
<a class="jxr_linenumber" name="88" href="#88">88</a>  <em class="jxr_comment">     * block.  Dual Transfer Queues support all of these modes, as</em>
<a class="jxr_linenumber" name="89" href="#89">89</a>  <em class="jxr_comment">     * dictated by callers.</em>
<a class="jxr_linenumber" name="90" href="#90">90</a>  <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="91" href="#91">91</a>  <em class="jxr_comment">     * A FIFO dual queue may be implemented using a variation of the</em>
<a class="jxr_linenumber" name="92" href="#92">92</a>  <em class="jxr_comment">     * Michael &amp; Scott (M&amp;S) lock-free queue algorithm</em>
<a class="jxr_linenumber" name="93" href="#93">93</a>  <em class="jxr_comment">     * (<a href="http://www.cs.rochester.edu/u/scott/papers/1996_PODC_queues.pdf)." target="alexandria_uri">http://www.cs.rochester.edu/u/scott/papers/1996_PODC_queues.pdf).</a></em>
<a class="jxr_linenumber" name="94" href="#94">94</a>  <em class="jxr_comment">     * It maintains two pointer fields, "head", pointing to a</em>
<a class="jxr_linenumber" name="95" href="#95">95</a>  <em class="jxr_comment">     * (matched) node that in turn points to the first actual</em>
<a class="jxr_linenumber" name="96" href="#96">96</a>  <em class="jxr_comment">     * (unmatched) queue node (or null if empty); and "tail" that</em>
<a class="jxr_linenumber" name="97" href="#97">97</a>  <em class="jxr_comment">     * points to the last node on the queue (or again null if</em>
<a class="jxr_linenumber" name="98" href="#98">98</a>  <em class="jxr_comment">     * empty). For example, here is a possible queue with four data</em>
<a class="jxr_linenumber" name="99" href="#99">99</a>  <em class="jxr_comment">     * elements:</em>
<a class="jxr_linenumber" name="100" href="#100">100</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="101" href="#101">101</a> <em class="jxr_comment">     *  head                tail</em>
<a class="jxr_linenumber" name="102" href="#102">102</a> <em class="jxr_comment">     *    |                   |</em>
<a class="jxr_linenumber" name="103" href="#103">103</a> <em class="jxr_comment">     *    v                   v</em>
<a class="jxr_linenumber" name="104" href="#104">104</a> <em class="jxr_comment">     *    M -&gt; U -&gt; U -&gt; U -&gt; U</em>
<a class="jxr_linenumber" name="105" href="#105">105</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="106" href="#106">106</a> <em class="jxr_comment">     * The M&amp;S queue algorithm is known to be prone to scalability and</em>
<a class="jxr_linenumber" name="107" href="#107">107</a> <em class="jxr_comment">     * overhead limitations when maintaining (via CAS) these head and</em>
<a class="jxr_linenumber" name="108" href="#108">108</a> <em class="jxr_comment">     * tail pointers. This has led to the development of</em>
<a class="jxr_linenumber" name="109" href="#109">109</a> <em class="jxr_comment">     * contention-reducing variants such as elimination arrays (see</em>
<a class="jxr_linenumber" name="110" href="#110">110</a> <em class="jxr_comment">     * Moir et al <a href="http://portal.acm.org/citation.cfm?id=1074013)" target="alexandria_uri">http://portal.acm.org/citation.cfm?id=1074013)</a> and</em>
<a class="jxr_linenumber" name="111" href="#111">111</a> <em class="jxr_comment">     * optimistic back pointers (see Ladan-Mozes &amp; Shavit</em>
<a class="jxr_linenumber" name="112" href="#112">112</a> <em class="jxr_comment">     * <a href="http://people.csail.mit.edu/edya/publications/OptimisticFIFOQueue-journal.pdf)." target="alexandria_uri">http://people.csail.mit.edu/edya/publications/OptimisticFIFOQueue-journal.pdf).</a></em>
<a class="jxr_linenumber" name="113" href="#113">113</a> <em class="jxr_comment">     * However, the nature of dual queues enables a simpler tactic for</em>
<a class="jxr_linenumber" name="114" href="#114">114</a> <em class="jxr_comment">     * improving M&amp;S-style implementations when dual-ness is needed.</em>
<a class="jxr_linenumber" name="115" href="#115">115</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="116" href="#116">116</a> <em class="jxr_comment">     * In a dual queue, each node must atomically maintain its match</em>
<a class="jxr_linenumber" name="117" href="#117">117</a> <em class="jxr_comment">     * status. While there are other possible variants, we implement</em>
<a class="jxr_linenumber" name="118" href="#118">118</a> <em class="jxr_comment">     * this here as: for a data-mode node, matching entails CASing an</em>
<a class="jxr_linenumber" name="119" href="#119">119</a> <em class="jxr_comment">     * "item" field from a non-null data value to null upon match, and</em>
<a class="jxr_linenumber" name="120" href="#120">120</a> <em class="jxr_comment">     * vice-versa for request nodes, CASing from null to a data</em>
<a class="jxr_linenumber" name="121" href="#121">121</a> <em class="jxr_comment">     * value. (Note that the linearization properties of this style of</em>
<a class="jxr_linenumber" name="122" href="#122">122</a> <em class="jxr_comment">     * queue are easy to verify -- elements are made available by</em>
<a class="jxr_linenumber" name="123" href="#123">123</a> <em class="jxr_comment">     * linking, and unavailable by matching.) Compared to plain M&amp;S</em>
<a class="jxr_linenumber" name="124" href="#124">124</a> <em class="jxr_comment">     * queues, this property of dual queues requires one additional</em>
<a class="jxr_linenumber" name="125" href="#125">125</a> <em class="jxr_comment">     * successful atomic operation per enq/deq pair. But it also</em>
<a class="jxr_linenumber" name="126" href="#126">126</a> <em class="jxr_comment">     * enables lower cost variants of queue maintenance mechanics. (A</em>
<a class="jxr_linenumber" name="127" href="#127">127</a> <em class="jxr_comment">     * variation of this idea applies even for non-dual queues that</em>
<a class="jxr_linenumber" name="128" href="#128">128</a> <em class="jxr_comment">     * support deletion of interior elements, such as</em>
<a class="jxr_linenumber" name="129" href="#129">129</a> <em class="jxr_comment">     * j.u.c.ConcurrentLinkedQueue.)</em>
<a class="jxr_linenumber" name="130" href="#130">130</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="131" href="#131">131</a> <em class="jxr_comment">     * Once a node is matched, its match status can never again</em>
<a class="jxr_linenumber" name="132" href="#132">132</a> <em class="jxr_comment">     * change.  We may thus arrange that the linked list of them</em>
<a class="jxr_linenumber" name="133" href="#133">133</a> <em class="jxr_comment">     * contain a prefix of zero or more matched nodes, followed by a</em>
<a class="jxr_linenumber" name="134" href="#134">134</a> <em class="jxr_comment">     * suffix of zero or more unmatched nodes. (Note that we allow</em>
<a class="jxr_linenumber" name="135" href="#135">135</a> <em class="jxr_comment">     * both the prefix and suffix to be zero length, which in turn</em>
<a class="jxr_linenumber" name="136" href="#136">136</a> <em class="jxr_comment">     * means that we do not use a dummy header.)  If we were not</em>
<a class="jxr_linenumber" name="137" href="#137">137</a> <em class="jxr_comment">     * concerned with either time or space efficiency, we could</em>
<a class="jxr_linenumber" name="138" href="#138">138</a> <em class="jxr_comment">     * correctly perform enqueue and dequeue operations by traversing</em>
<a class="jxr_linenumber" name="139" href="#139">139</a> <em class="jxr_comment">     * from a pointer to the initial node; CASing the item of the</em>
<a class="jxr_linenumber" name="140" href="#140">140</a> <em class="jxr_comment">     * first unmatched node on match and CASing the next field of the</em>
<a class="jxr_linenumber" name="141" href="#141">141</a> <em class="jxr_comment">     * trailing node on appends. (Plus some special-casing when</em>
<a class="jxr_linenumber" name="142" href="#142">142</a> <em class="jxr_comment">     * initially empty).  While this would be a terrible idea in</em>
<a class="jxr_linenumber" name="143" href="#143">143</a> <em class="jxr_comment">     * itself, it does have the benefit of not requiring ANY atomic</em>
<a class="jxr_linenumber" name="144" href="#144">144</a> <em class="jxr_comment">     * updates on head/tail fields.</em>
<a class="jxr_linenumber" name="145" href="#145">145</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="146" href="#146">146</a> <em class="jxr_comment">     * We introduce here an approach that lies between the extremes of</em>
<a class="jxr_linenumber" name="147" href="#147">147</a> <em class="jxr_comment">     * never versus always updating queue (head and tail) pointers.</em>
<a class="jxr_linenumber" name="148" href="#148">148</a> <em class="jxr_comment">     * This offers a tradeoff between sometimes requiring extra</em>
<a class="jxr_linenumber" name="149" href="#149">149</a> <em class="jxr_comment">     * traversal steps to locate the first and/or last unmatched</em>
<a class="jxr_linenumber" name="150" href="#150">150</a> <em class="jxr_comment">     * nodes, versus the reduced overhead and contention of fewer</em>
<a class="jxr_linenumber" name="151" href="#151">151</a> <em class="jxr_comment">     * updates to queue pointers. For example, a possible snapshot of</em>
<a class="jxr_linenumber" name="152" href="#152">152</a> <em class="jxr_comment">     * a queue is:</em>
<a class="jxr_linenumber" name="153" href="#153">153</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="154" href="#154">154</a> <em class="jxr_comment">     *  head           tail</em>
<a class="jxr_linenumber" name="155" href="#155">155</a> <em class="jxr_comment">     *    |              |</em>
<a class="jxr_linenumber" name="156" href="#156">156</a> <em class="jxr_comment">     *    v              v</em>
<a class="jxr_linenumber" name="157" href="#157">157</a> <em class="jxr_comment">     *    M -&gt; M -&gt; U -&gt; U -&gt; U -&gt; U</em>
<a class="jxr_linenumber" name="158" href="#158">158</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="159" href="#159">159</a> <em class="jxr_comment">     * The best value for this "slack" (the targeted maximum distance</em>
<a class="jxr_linenumber" name="160" href="#160">160</a> <em class="jxr_comment">     * between the value of "head" and the first unmatched node, and</em>
<a class="jxr_linenumber" name="161" href="#161">161</a> <em class="jxr_comment">     * similarly for "tail") is an empirical matter. We have found</em>
<a class="jxr_linenumber" name="162" href="#162">162</a> <em class="jxr_comment">     * that using very small constants in the range of 1-3 work best</em>
<a class="jxr_linenumber" name="163" href="#163">163</a> <em class="jxr_comment">     * over a range of platforms. Larger values introduce increasing</em>
<a class="jxr_linenumber" name="164" href="#164">164</a> <em class="jxr_comment">     * costs of cache misses and risks of long traversal chains, while</em>
<a class="jxr_linenumber" name="165" href="#165">165</a> <em class="jxr_comment">     * smaller values increase CAS contention and overhead.</em>
<a class="jxr_linenumber" name="166" href="#166">166</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="167" href="#167">167</a> <em class="jxr_comment">     * Dual queues with slack differ from plain M&amp;S dual queues by</em>
<a class="jxr_linenumber" name="168" href="#168">168</a> <em class="jxr_comment">     * virtue of only sometimes updating head or tail pointers when</em>
<a class="jxr_linenumber" name="169" href="#169">169</a> <em class="jxr_comment">     * matching, appending, or even traversing nodes; in order to</em>
<a class="jxr_linenumber" name="170" href="#170">170</a> <em class="jxr_comment">     * maintain a targeted slack.  The idea of "sometimes" may be</em>
<a class="jxr_linenumber" name="171" href="#171">171</a> <em class="jxr_comment">     * operationalized in several ways. The simplest is to use a</em>
<a class="jxr_linenumber" name="172" href="#172">172</a> <em class="jxr_comment">     * per-operation counter incremented on each traversal step, and</em>
<a class="jxr_linenumber" name="173" href="#173">173</a> <em class="jxr_comment">     * to try (via CAS) to update the associated queue pointer</em>
<a class="jxr_linenumber" name="174" href="#174">174</a> <em class="jxr_comment">     * whenever the count exceeds a threshold. Another, that requires</em>
<a class="jxr_linenumber" name="175" href="#175">175</a> <em class="jxr_comment">     * more overhead, is to use random number generators to update</em>
<a class="jxr_linenumber" name="176" href="#176">176</a> <em class="jxr_comment">     * with a given probability per traversal step.</em>
<a class="jxr_linenumber" name="177" href="#177">177</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="178" href="#178">178</a> <em class="jxr_comment">     * In any strategy along these lines, because CASes updating</em>
<a class="jxr_linenumber" name="179" href="#179">179</a> <em class="jxr_comment">     * fields may fail, the actual slack may exceed targeted</em>
<a class="jxr_linenumber" name="180" href="#180">180</a> <em class="jxr_comment">     * slack. However, they may be retried at any time to maintain</em>
<a class="jxr_linenumber" name="181" href="#181">181</a> <em class="jxr_comment">     * targets.  Even when using very small slack values, this</em>
<a class="jxr_linenumber" name="182" href="#182">182</a> <em class="jxr_comment">     * approach works well for dual queues because it allows all</em>
<a class="jxr_linenumber" name="183" href="#183">183</a> <em class="jxr_comment">     * operations up to the point of matching or appending an item</em>
<a class="jxr_linenumber" name="184" href="#184">184</a> <em class="jxr_comment">     * (hence potentially allowing progress by another thread) to be</em>
<a class="jxr_linenumber" name="185" href="#185">185</a> <em class="jxr_comment">     * read-only, thus not introducing any further contention. As</em>
<a class="jxr_linenumber" name="186" href="#186">186</a> <em class="jxr_comment">     * described below, we implement this by performing slack</em>
<a class="jxr_linenumber" name="187" href="#187">187</a> <em class="jxr_comment">     * maintenance retries only after these points.</em>
<a class="jxr_linenumber" name="188" href="#188">188</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="189" href="#189">189</a> <em class="jxr_comment">     * As an accompaniment to such techniques, traversal overhead can</em>
<a class="jxr_linenumber" name="190" href="#190">190</a> <em class="jxr_comment">     * be further reduced without increasing contention of head</em>
<a class="jxr_linenumber" name="191" href="#191">191</a> <em class="jxr_comment">     * pointer updates: Threads may sometimes shortcut the "next" link</em>
<a class="jxr_linenumber" name="192" href="#192">192</a> <em class="jxr_comment">     * path from the current "head" node to be closer to the currently</em>
<a class="jxr_linenumber" name="193" href="#193">193</a> <em class="jxr_comment">     * known first unmatched node, and similarly for tail. Again, this</em>
<a class="jxr_linenumber" name="194" href="#194">194</a> <em class="jxr_comment">     * may be triggered with using thresholds or randomization.</em>
<a class="jxr_linenumber" name="195" href="#195">195</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="196" href="#196">196</a> <em class="jxr_comment">     * These ideas must be further extended to avoid unbounded amounts</em>
<a class="jxr_linenumber" name="197" href="#197">197</a> <em class="jxr_comment">     * of costly-to-reclaim garbage caused by the sequential "next"</em>
<a class="jxr_linenumber" name="198" href="#198">198</a> <em class="jxr_comment">     * links of nodes starting at old forgotten head nodes: As first</em>
<a class="jxr_linenumber" name="199" href="#199">199</a> <em class="jxr_comment">     * described in detail by Boehm</em>
<a class="jxr_linenumber" name="200" href="#200">200</a> <em class="jxr_comment">     * (<a href="http://portal.acm.org/citation.cfm?doid=503272.503282)" target="alexandria_uri">http://portal.acm.org/citation.cfm?doid=503272.503282)</a> if a GC</em>
<a class="jxr_linenumber" name="201" href="#201">201</a> <em class="jxr_comment">     * delays noticing that any arbitrarily old node has become</em>
<a class="jxr_linenumber" name="202" href="#202">202</a> <em class="jxr_comment">     * garbage, all newer dead nodes will also be unreclaimed.</em>
<a class="jxr_linenumber" name="203" href="#203">203</a> <em class="jxr_comment">     * (Similar issues arise in non-GC environments.)  To cope with</em>
<a class="jxr_linenumber" name="204" href="#204">204</a> <em class="jxr_comment">     * this in our implementation, upon CASing to advance the head</em>
<a class="jxr_linenumber" name="205" href="#205">205</a> <em class="jxr_comment">     * pointer, we set the "next" link of the previous head to point</em>
<a class="jxr_linenumber" name="206" href="#206">206</a> <em class="jxr_comment">     * only to itself; thus limiting the length of connected dead lists.</em>
<a class="jxr_linenumber" name="207" href="#207">207</a> <em class="jxr_comment">     * (We also take similar care to wipe out possibly garbage</em>
<a class="jxr_linenumber" name="208" href="#208">208</a> <em class="jxr_comment">     * retaining values held in other Node fields.)  However, doing so</em>
<a class="jxr_linenumber" name="209" href="#209">209</a> <em class="jxr_comment">     * adds some further complexity to traversal: If any "next"</em>
<a class="jxr_linenumber" name="210" href="#210">210</a> <em class="jxr_comment">     * pointer links to itself, it indicates that the current thread</em>
<a class="jxr_linenumber" name="211" href="#211">211</a> <em class="jxr_comment">     * has lagged behind a head-update, and so the traversal must</em>
<a class="jxr_linenumber" name="212" href="#212">212</a> <em class="jxr_comment">     * continue from the "head".  Traversals trying to find the</em>
<a class="jxr_linenumber" name="213" href="#213">213</a> <em class="jxr_comment">     * current tail starting from "tail" may also encounter</em>
<a class="jxr_linenumber" name="214" href="#214">214</a> <em class="jxr_comment">     * self-links, in which case they also continue at "head".</em>
<a class="jxr_linenumber" name="215" href="#215">215</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="216" href="#216">216</a> <em class="jxr_comment">     * It is tempting in slack-based scheme to not even use CAS for</em>
<a class="jxr_linenumber" name="217" href="#217">217</a> <em class="jxr_comment">     * updates (similarly to Ladan-Mozes &amp; Shavit). However, this</em>
<a class="jxr_linenumber" name="218" href="#218">218</a> <em class="jxr_comment">     * cannot be done for head updates under the above link-forgetting</em>
<a class="jxr_linenumber" name="219" href="#219">219</a> <em class="jxr_comment">     * mechanics because an update may leave head at a detached node.</em>
<a class="jxr_linenumber" name="220" href="#220">220</a> <em class="jxr_comment">     * And while direct writes are possible for tail updates, they</em>
<a class="jxr_linenumber" name="221" href="#221">221</a> <em class="jxr_comment">     * increase the risk of long retraversals, and hence long garbage</em>
<a class="jxr_linenumber" name="222" href="#222">222</a> <em class="jxr_comment">     * chains, which can be much more costly than is worthwhile</em>
<a class="jxr_linenumber" name="223" href="#223">223</a> <em class="jxr_comment">     * considering that the cost difference of performing a CAS vs</em>
<a class="jxr_linenumber" name="224" href="#224">224</a> <em class="jxr_comment">     * write is smaller when they are not triggered on each operation</em>
<a class="jxr_linenumber" name="225" href="#225">225</a> <em class="jxr_comment">     * (especially considering that writes and CASes equally require</em>
<a class="jxr_linenumber" name="226" href="#226">226</a> <em class="jxr_comment">     * additional GC bookkeeping ("write barriers") that are sometimes</em>
<a class="jxr_linenumber" name="227" href="#227">227</a> <em class="jxr_comment">     * more costly than the writes themselves because of contention).</em>
<a class="jxr_linenumber" name="228" href="#228">228</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="229" href="#229">229</a> <em class="jxr_comment">     * *** Overview of implementation ***</em>
<a class="jxr_linenumber" name="230" href="#230">230</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="231" href="#231">231</a> <em class="jxr_comment">     * We use a threshold-based approach to updates, with a slack</em>
<a class="jxr_linenumber" name="232" href="#232">232</a> <em class="jxr_comment">     * threshold of two -- that is, we update head/tail when the</em>
<a class="jxr_linenumber" name="233" href="#233">233</a> <em class="jxr_comment">     * current pointer appears to be two or more steps away from the</em>
<a class="jxr_linenumber" name="234" href="#234">234</a> <em class="jxr_comment">     * first/last node. The slack value is hard-wired: a path greater</em>
<a class="jxr_linenumber" name="235" href="#235">235</a> <em class="jxr_comment">     * than one is naturally implemented by checking equality of</em>
<a class="jxr_linenumber" name="236" href="#236">236</a> <em class="jxr_comment">     * traversal pointers except when the list has only one element,</em>
<a class="jxr_linenumber" name="237" href="#237">237</a> <em class="jxr_comment">     * in which case we keep slack threshold at one. Avoiding tracking</em>
<a class="jxr_linenumber" name="238" href="#238">238</a> <em class="jxr_comment">     * explicit counts across method calls slightly simplifies an</em>
<a class="jxr_linenumber" name="239" href="#239">239</a> <em class="jxr_comment">     * already-messy implementation. Using randomization would</em>
<a class="jxr_linenumber" name="240" href="#240">240</a> <em class="jxr_comment">     * probably work better if there were a low-quality dirt-cheap</em>
<a class="jxr_linenumber" name="241" href="#241">241</a> <em class="jxr_comment">     * per-thread one available, but even ThreadLocalRandom is too</em>
<a class="jxr_linenumber" name="242" href="#242">242</a> <em class="jxr_comment">     * heavy for these purposes.</em>
<a class="jxr_linenumber" name="243" href="#243">243</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="244" href="#244">244</a> <em class="jxr_comment">     * With such a small slack threshold value, it is not worthwhile</em>
<a class="jxr_linenumber" name="245" href="#245">245</a> <em class="jxr_comment">     * to augment this with path short-circuiting (i.e., unsplicing</em>
<a class="jxr_linenumber" name="246" href="#246">246</a> <em class="jxr_comment">     * interior nodes) except in the case of cancellation/removal (see</em>
<a class="jxr_linenumber" name="247" href="#247">247</a> <em class="jxr_comment">     * below).</em>
<a class="jxr_linenumber" name="248" href="#248">248</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="249" href="#249">249</a> <em class="jxr_comment">     * We allow both the head and tail fields to be null before any</em>
<a class="jxr_linenumber" name="250" href="#250">250</a> <em class="jxr_comment">     * nodes are enqueued; initializing upon first append.  This</em>
<a class="jxr_linenumber" name="251" href="#251">251</a> <em class="jxr_comment">     * simplifies some other logic, as well as providing more</em>
<a class="jxr_linenumber" name="252" href="#252">252</a> <em class="jxr_comment">     * efficient explicit control paths instead of letting JVMs insert</em>
<a class="jxr_linenumber" name="253" href="#253">253</a> <em class="jxr_comment">     * implicit NullPointerExceptions when they are null.  While not</em>
<a class="jxr_linenumber" name="254" href="#254">254</a> <em class="jxr_comment">     * currently fully implemented, we also leave open the possibility</em>
<a class="jxr_linenumber" name="255" href="#255">255</a> <em class="jxr_comment">     * of re-nulling these fields when empty (which is complicated to</em>
<a class="jxr_linenumber" name="256" href="#256">256</a> <em class="jxr_comment">     * arrange, for little benefit.)</em>
<a class="jxr_linenumber" name="257" href="#257">257</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="258" href="#258">258</a> <em class="jxr_comment">     * All enqueue/dequeue operations are handled by the single method</em>
<a class="jxr_linenumber" name="259" href="#259">259</a> <em class="jxr_comment">     * "xfer" with parameters indicating whether to act as some form</em>
<a class="jxr_linenumber" name="260" href="#260">260</a> <em class="jxr_comment">     * of offer, put, poll, take, or transfer (each possibly with</em>
<a class="jxr_linenumber" name="261" href="#261">261</a> <em class="jxr_comment">     * timeout). The relative complexity of using one monolithic</em>
<a class="jxr_linenumber" name="262" href="#262">262</a> <em class="jxr_comment">     * method outweighs the code bulk and maintenance problems of</em>
<a class="jxr_linenumber" name="263" href="#263">263</a> <em class="jxr_comment">     * using separate methods for each case.</em>
<a class="jxr_linenumber" name="264" href="#264">264</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="265" href="#265">265</a> <em class="jxr_comment">     * Operation consists of up to three phases. The first is</em>
<a class="jxr_linenumber" name="266" href="#266">266</a> <em class="jxr_comment">     * implemented within method xfer, the second in tryAppend, and</em>
<a class="jxr_linenumber" name="267" href="#267">267</a> <em class="jxr_comment">     * the third in method awaitMatch.</em>
<a class="jxr_linenumber" name="268" href="#268">268</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="269" href="#269">269</a> <em class="jxr_comment">     * 1. Try to match an existing node</em>
<a class="jxr_linenumber" name="270" href="#270">270</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="271" href="#271">271</a> <em class="jxr_comment">     *    Starting at head, skip already-matched nodes until finding</em>
<a class="jxr_linenumber" name="272" href="#272">272</a> <em class="jxr_comment">     *    an unmatched node of opposite mode, if one exists, in which</em>
<a class="jxr_linenumber" name="273" href="#273">273</a> <em class="jxr_comment">     *    case matching it and returning, also if necessary updating</em>
<a class="jxr_linenumber" name="274" href="#274">274</a> <em class="jxr_comment">     *    head to one past the matched node (or the node itself if the</em>
<a class="jxr_linenumber" name="275" href="#275">275</a> <em class="jxr_comment">     *    list has no other unmatched nodes). If the CAS misses, then</em>
<a class="jxr_linenumber" name="276" href="#276">276</a> <em class="jxr_comment">     *    a loop retries advancing head by two steps until either</em>
<a class="jxr_linenumber" name="277" href="#277">277</a> <em class="jxr_comment">     *    success or the slack is at most two. By requiring that each</em>
<a class="jxr_linenumber" name="278" href="#278">278</a> <em class="jxr_comment">     *    attempt advances head by two (if applicable), we ensure that</em>
<a class="jxr_linenumber" name="279" href="#279">279</a> <em class="jxr_comment">     *    the slack does not grow without bound. Traversals also check</em>
<a class="jxr_linenumber" name="280" href="#280">280</a> <em class="jxr_comment">     *    if the initial head is now off-list, in which case they</em>
<a class="jxr_linenumber" name="281" href="#281">281</a> <em class="jxr_comment">     *    start at the new head.</em>
<a class="jxr_linenumber" name="282" href="#282">282</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="283" href="#283">283</a> <em class="jxr_comment">     *    If no candidates are found and the call was untimed</em>
<a class="jxr_linenumber" name="284" href="#284">284</a> <em class="jxr_comment">     *    poll/offer, (argument "how" is NOW) return.</em>
<a class="jxr_linenumber" name="285" href="#285">285</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="286" href="#286">286</a> <em class="jxr_comment">     * 2. Try to append a new node (method tryAppend)</em>
<a class="jxr_linenumber" name="287" href="#287">287</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="288" href="#288">288</a> <em class="jxr_comment">     *    Starting at current tail pointer, find the actual last node</em>
<a class="jxr_linenumber" name="289" href="#289">289</a> <em class="jxr_comment">     *    and try to append a new node (or if head was null, establish</em>
<a class="jxr_linenumber" name="290" href="#290">290</a> <em class="jxr_comment">     *    the first node). Nodes can be appended only if their</em>
<a class="jxr_linenumber" name="291" href="#291">291</a> <em class="jxr_comment">     *    predecessors are either already matched or are of the same</em>
<a class="jxr_linenumber" name="292" href="#292">292</a> <em class="jxr_comment">     *    mode. If we detect otherwise, then a new node with opposite</em>
<a class="jxr_linenumber" name="293" href="#293">293</a> <em class="jxr_comment">     *    mode must have been appended during traversal, so we must</em>
<a class="jxr_linenumber" name="294" href="#294">294</a> <em class="jxr_comment">     *    restart at phase 1. The traversal and update steps are</em>
<a class="jxr_linenumber" name="295" href="#295">295</a> <em class="jxr_comment">     *    otherwise similar to phase 1: Retrying upon CAS misses and</em>
<a class="jxr_linenumber" name="296" href="#296">296</a> <em class="jxr_comment">     *    checking for staleness.  In particular, if a self-link is</em>
<a class="jxr_linenumber" name="297" href="#297">297</a> <em class="jxr_comment">     *    encountered, then we can safely jump to a node on the list</em>
<a class="jxr_linenumber" name="298" href="#298">298</a> <em class="jxr_comment">     *    by continuing the traversal at current head.</em>
<a class="jxr_linenumber" name="299" href="#299">299</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="300" href="#300">300</a> <em class="jxr_comment">     *    On successful append, if the call was ASYNC, return.</em>
<a class="jxr_linenumber" name="301" href="#301">301</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="302" href="#302">302</a> <em class="jxr_comment">     * 3. Await match or cancellation (method awaitMatch)</em>
<a class="jxr_linenumber" name="303" href="#303">303</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="304" href="#304">304</a> <em class="jxr_comment">     *    Wait for another thread to match node; instead cancelling if</em>
<a class="jxr_linenumber" name="305" href="#305">305</a> <em class="jxr_comment">     *    the current thread was interrupted or the wait timed out. On</em>
<a class="jxr_linenumber" name="306" href="#306">306</a> <em class="jxr_comment">     *    multiprocessors, we use front-of-queue spinning: If a node</em>
<a class="jxr_linenumber" name="307" href="#307">307</a> <em class="jxr_comment">     *    appears to be the first unmatched node in the queue, it</em>
<a class="jxr_linenumber" name="308" href="#308">308</a> <em class="jxr_comment">     *    spins a bit before blocking. In either case, before blocking</em>
<a class="jxr_linenumber" name="309" href="#309">309</a> <em class="jxr_comment">     *    it tries to unsplice any nodes between the current "head"</em>
<a class="jxr_linenumber" name="310" href="#310">310</a> <em class="jxr_comment">     *    and the first unmatched node.</em>
<a class="jxr_linenumber" name="311" href="#311">311</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="312" href="#312">312</a> <em class="jxr_comment">     *    Front-of-queue spinning vastly improves performance of</em>
<a class="jxr_linenumber" name="313" href="#313">313</a> <em class="jxr_comment">     *    heavily contended queues. And so long as it is relatively</em>
<a class="jxr_linenumber" name="314" href="#314">314</a> <em class="jxr_comment">     *    brief and "quiet", spinning does not much impact performance</em>
<a class="jxr_linenumber" name="315" href="#315">315</a> <em class="jxr_comment">     *    of less-contended queues.  During spins threads check their</em>
<a class="jxr_linenumber" name="316" href="#316">316</a> <em class="jxr_comment">     *    interrupt status and generate a thread-local random number</em>
<a class="jxr_linenumber" name="317" href="#317">317</a> <em class="jxr_comment">     *    to decide to occasionally perform a Thread.yield. While</em>
<a class="jxr_linenumber" name="318" href="#318">318</a> <em class="jxr_comment">     *    yield has underdefined specs, we assume that might it help,</em>
<a class="jxr_linenumber" name="319" href="#319">319</a> <em class="jxr_comment">     *    and will not hurt in limiting impact of spinning on busy</em>
<a class="jxr_linenumber" name="320" href="#320">320</a> <em class="jxr_comment">     *    systems.  We also use smaller (1/2) spins for nodes that are</em>
<a class="jxr_linenumber" name="321" href="#321">321</a> <em class="jxr_comment">     *    not known to be front but whose predecessors have not</em>
<a class="jxr_linenumber" name="322" href="#322">322</a> <em class="jxr_comment">     *    blocked -- these "chained" spins avoid artifacts of</em>
<a class="jxr_linenumber" name="323" href="#323">323</a> <em class="jxr_comment">     *    front-of-queue rules which otherwise lead to alternating</em>
<a class="jxr_linenumber" name="324" href="#324">324</a> <em class="jxr_comment">     *    nodes spinning vs blocking. Further, front threads that</em>
<a class="jxr_linenumber" name="325" href="#325">325</a> <em class="jxr_comment">     *    represent phase changes (from data to request node or vice</em>
<a class="jxr_linenumber" name="326" href="#326">326</a> <em class="jxr_comment">     *    versa) compared to their predecessors receive additional</em>
<a class="jxr_linenumber" name="327" href="#327">327</a> <em class="jxr_comment">     *    chained spins, reflecting longer paths typically required to</em>
<a class="jxr_linenumber" name="328" href="#328">328</a> <em class="jxr_comment">     *    unblock threads during phase changes.</em>
<a class="jxr_linenumber" name="329" href="#329">329</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="330" href="#330">330</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="331" href="#331">331</a> <em class="jxr_comment">     * ** Unlinking removed interior nodes **</em>
<a class="jxr_linenumber" name="332" href="#332">332</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="333" href="#333">333</a> <em class="jxr_comment">     * In addition to minimizing garbage retention via self-linking</em>
<a class="jxr_linenumber" name="334" href="#334">334</a> <em class="jxr_comment">     * described above, we also unlink removed interior nodes. These</em>
<a class="jxr_linenumber" name="335" href="#335">335</a> <em class="jxr_comment">     * may arise due to timed out or interrupted waits, or calls to</em>
<a class="jxr_linenumber" name="336" href="#336">336</a> <em class="jxr_comment">     * remove(x) or Iterator.remove.  Normally, given a node that was</em>
<a class="jxr_linenumber" name="337" href="#337">337</a> <em class="jxr_comment">     * at one time known to be the predecessor of some node s that is</em>
<a class="jxr_linenumber" name="338" href="#338">338</a> <em class="jxr_comment">     * to be removed, we can unsplice s by CASing the next field of</em>
<a class="jxr_linenumber" name="339" href="#339">339</a> <em class="jxr_comment">     * its predecessor if it still points to s (otherwise s must</em>
<a class="jxr_linenumber" name="340" href="#340">340</a> <em class="jxr_comment">     * already have been removed or is now offlist). But there are two</em>
<a class="jxr_linenumber" name="341" href="#341">341</a> <em class="jxr_comment">     * situations in which we cannot guarantee to make node s</em>
<a class="jxr_linenumber" name="342" href="#342">342</a> <em class="jxr_comment">     * unreachable in this way: (1) If s is the trailing node of list</em>
<a class="jxr_linenumber" name="343" href="#343">343</a> <em class="jxr_comment">     * (i.e., with null next), then it is pinned as the target node</em>
<a class="jxr_linenumber" name="344" href="#344">344</a> <em class="jxr_comment">     * for appends, so can only be removed later after other nodes are</em>
<a class="jxr_linenumber" name="345" href="#345">345</a> <em class="jxr_comment">     * appended. (2) We cannot necessarily unlink s given a</em>
<a class="jxr_linenumber" name="346" href="#346">346</a> <em class="jxr_comment">     * predecessor node that is matched (including the case of being</em>
<a class="jxr_linenumber" name="347" href="#347">347</a> <em class="jxr_comment">     * cancelled): the predecessor may already be unspliced, in which</em>
<a class="jxr_linenumber" name="348" href="#348">348</a> <em class="jxr_comment">     * case some previous reachable node may still point to s.</em>
<a class="jxr_linenumber" name="349" href="#349">349</a> <em class="jxr_comment">     * (For further explanation see Herlihy &amp; Shavit "The Art of</em>
<a class="jxr_linenumber" name="350" href="#350">350</a> <em class="jxr_comment">     * Multiprocessor Programming" chapter 9).  Although, in both</em>
<a class="jxr_linenumber" name="351" href="#351">351</a> <em class="jxr_comment">     * cases, we can rule out the need for further action if either s</em>
<a class="jxr_linenumber" name="352" href="#352">352</a> <em class="jxr_comment">     * or its predecessor are (or can be made to be) at, or fall off</em>
<a class="jxr_linenumber" name="353" href="#353">353</a> <em class="jxr_comment">     * from, the head of list.</em>
<a class="jxr_linenumber" name="354" href="#354">354</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="355" href="#355">355</a> <em class="jxr_comment">     * Without taking these into account, it would be possible for an</em>
<a class="jxr_linenumber" name="356" href="#356">356</a> <em class="jxr_comment">     * unbounded number of supposedly removed nodes to remain</em>
<a class="jxr_linenumber" name="357" href="#357">357</a> <em class="jxr_comment">     * reachable.  Situations leading to such buildup are uncommon but</em>
<a class="jxr_linenumber" name="358" href="#358">358</a> <em class="jxr_comment">     * can occur in practice; for example when a series of short timed</em>
<a class="jxr_linenumber" name="359" href="#359">359</a> <em class="jxr_comment">     * calls to poll repeatedly time out but never otherwise fall off</em>
<a class="jxr_linenumber" name="360" href="#360">360</a> <em class="jxr_comment">     * the list because of an untimed call to take at the front of the</em>
<a class="jxr_linenumber" name="361" href="#361">361</a> <em class="jxr_comment">     * queue.</em>
<a class="jxr_linenumber" name="362" href="#362">362</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="363" href="#363">363</a> <em class="jxr_comment">     * When these cases arise, rather than always retraversing the</em>
<a class="jxr_linenumber" name="364" href="#364">364</a> <em class="jxr_comment">     * entire list to find an actual predecessor to unlink (which</em>
<a class="jxr_linenumber" name="365" href="#365">365</a> <em class="jxr_comment">     * won't help for case (1) anyway), we record a conservative</em>
<a class="jxr_linenumber" name="366" href="#366">366</a> <em class="jxr_comment">     * estimate of possible unsplice failures (in "sweepVotes").</em>
<a class="jxr_linenumber" name="367" href="#367">367</a> <em class="jxr_comment">     * We trigger a full sweep when the estimate exceeds a threshold</em>
<a class="jxr_linenumber" name="368" href="#368">368</a> <em class="jxr_comment">     * ("SWEEP_THRESHOLD") indicating the maximum number of estimated</em>
<a class="jxr_linenumber" name="369" href="#369">369</a> <em class="jxr_comment">     * removal failures to tolerate before sweeping through, unlinking</em>
<a class="jxr_linenumber" name="370" href="#370">370</a> <em class="jxr_comment">     * cancelled nodes that were not unlinked upon initial removal.</em>
<a class="jxr_linenumber" name="371" href="#371">371</a> <em class="jxr_comment">     * We perform sweeps by the thread hitting threshold (rather than</em>
<a class="jxr_linenumber" name="372" href="#372">372</a> <em class="jxr_comment">     * background threads or by spreading work to other threads)</em>
<a class="jxr_linenumber" name="373" href="#373">373</a> <em class="jxr_comment">     * because in the main contexts in which removal occurs, the</em>
<a class="jxr_linenumber" name="374" href="#374">374</a> <em class="jxr_comment">     * caller is already timed-out, cancelled, or performing a</em>
<a class="jxr_linenumber" name="375" href="#375">375</a> <em class="jxr_comment">     * potentially O(n) operation (e.g. remove(x)), none of which are</em>
<a class="jxr_linenumber" name="376" href="#376">376</a> <em class="jxr_comment">     * time-critical enough to warrant the overhead that alternatives</em>
<a class="jxr_linenumber" name="377" href="#377">377</a> <em class="jxr_comment">     * would impose on other threads.</em>
<a class="jxr_linenumber" name="378" href="#378">378</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="379" href="#379">379</a> <em class="jxr_comment">     * Because the sweepVotes estimate is conservative, and because</em>
<a class="jxr_linenumber" name="380" href="#380">380</a> <em class="jxr_comment">     * nodes become unlinked "naturally" as they fall off the head of</em>
<a class="jxr_linenumber" name="381" href="#381">381</a> <em class="jxr_comment">     * the queue, and because we allow votes to accumulate even while</em>
<a class="jxr_linenumber" name="382" href="#382">382</a> <em class="jxr_comment">     * sweeps are in progress, there are typically significantly fewer</em>
<a class="jxr_linenumber" name="383" href="#383">383</a> <em class="jxr_comment">     * such nodes than estimated.  Choice of a threshold value</em>
<a class="jxr_linenumber" name="384" href="#384">384</a> <em class="jxr_comment">     * balances the likelihood of wasted effort and contention, versus</em>
<a class="jxr_linenumber" name="385" href="#385">385</a> <em class="jxr_comment">     * providing a worst-case bound on retention of interior nodes in</em>
<a class="jxr_linenumber" name="386" href="#386">386</a> <em class="jxr_comment">     * quiescent queues. The value defined below was chosen</em>
<a class="jxr_linenumber" name="387" href="#387">387</a> <em class="jxr_comment">     * empirically to balance these under various timeout scenarios.</em>
<a class="jxr_linenumber" name="388" href="#388">388</a> <em class="jxr_comment">     *</em>
<a class="jxr_linenumber" name="389" href="#389">389</a> <em class="jxr_comment">     * Note that we cannot self-link unlinked interior nodes during</em>
<a class="jxr_linenumber" name="390" href="#390">390</a> <em class="jxr_comment">     * sweeps. However, the associated garbage chains terminate when</em>
<a class="jxr_linenumber" name="391" href="#391">391</a> <em class="jxr_comment">     * some successor ultimately falls off the head of the list and is</em>
<a class="jxr_linenumber" name="392" href="#392">392</a> <em class="jxr_comment">     * self-linked.</em>
<a class="jxr_linenumber" name="393" href="#393">393</a> <em class="jxr_comment">     */</em>
<a class="jxr_linenumber" name="394" href="#394">394</a> 
<a class="jxr_linenumber" name="395" href="#395">395</a>     <em class="jxr_javadoccomment">/**</em><em class="jxr_javadoccomment"> True if on multiprocessor */</em>
<a class="jxr_linenumber" name="396" href="#396">396</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> MP =
<a class="jxr_linenumber" name="397" href="#397">397</a>         Runtime.getRuntime().availableProcessors() &gt; 1;
<a class="jxr_linenumber" name="398" href="#398">398</a> 
<a class="jxr_linenumber" name="399" href="#399">399</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="400" href="#400">400</a> <em class="jxr_javadoccomment">     * The number of times to spin (with randomly interspersed calls</em>
<a class="jxr_linenumber" name="401" href="#401">401</a> <em class="jxr_javadoccomment">     * to Thread.yield) on multiprocessor before blocking when a node</em>
<a class="jxr_linenumber" name="402" href="#402">402</a> <em class="jxr_javadoccomment">     * is apparently the first waiter in the queue.  See above for</em>
<a class="jxr_linenumber" name="403" href="#403">403</a> <em class="jxr_javadoccomment">     * explanation. Must be a power of two. The value is empirically</em>
<a class="jxr_linenumber" name="404" href="#404">404</a> <em class="jxr_javadoccomment">     * derived -- it works pretty well across a variety of processors,</em>
<a class="jxr_linenumber" name="405" href="#405">405</a> <em class="jxr_javadoccomment">     * numbers of CPUs, and OSes.</em>
<a class="jxr_linenumber" name="406" href="#406">406</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="407" href="#407">407</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> FRONT_SPINS   = 1 &lt;&lt; 7;
<a class="jxr_linenumber" name="408" href="#408">408</a> 
<a class="jxr_linenumber" name="409" href="#409">409</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="410" href="#410">410</a> <em class="jxr_javadoccomment">     * The number of times to spin before blocking when a node is</em>
<a class="jxr_linenumber" name="411" href="#411">411</a> <em class="jxr_javadoccomment">     * preceded by another node that is apparently spinning.  Also</em>
<a class="jxr_linenumber" name="412" href="#412">412</a> <em class="jxr_javadoccomment">     * serves as an increment to FRONT_SPINS on phase changes, and as</em>
<a class="jxr_linenumber" name="413" href="#413">413</a> <em class="jxr_javadoccomment">     * base average frequency for yielding during spins. Must be a</em>
<a class="jxr_linenumber" name="414" href="#414">414</a> <em class="jxr_javadoccomment">     * power of two.</em>
<a class="jxr_linenumber" name="415" href="#415">415</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="416" href="#416">416</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> CHAINED_SPINS = FRONT_SPINS &gt;&gt;&gt; 1;
<a class="jxr_linenumber" name="417" href="#417">417</a> 
<a class="jxr_linenumber" name="418" href="#418">418</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="419" href="#419">419</a> <em class="jxr_javadoccomment">     * The maximum number of estimated removal failures (sweepVotes)</em>
<a class="jxr_linenumber" name="420" href="#420">420</a> <em class="jxr_javadoccomment">     * to tolerate before sweeping through the queue unlinking</em>
<a class="jxr_linenumber" name="421" href="#421">421</a> <em class="jxr_javadoccomment">     * cancelled nodes that were not unlinked upon initial</em>
<a class="jxr_linenumber" name="422" href="#422">422</a> <em class="jxr_javadoccomment">     * removal. See above for explanation. The value must be at least</em>
<a class="jxr_linenumber" name="423" href="#423">423</a> <em class="jxr_javadoccomment">     * two to avoid useless sweeps when removing trailing nodes.</em>
<a class="jxr_linenumber" name="424" href="#424">424</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="425" href="#425">425</a>     <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> SWEEP_THRESHOLD = 32;
<a class="jxr_linenumber" name="426" href="#426">426</a> 
<a class="jxr_linenumber" name="427" href="#427">427</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="428" href="#428">428</a> <em class="jxr_javadoccomment">     * Queue nodes. Uses Object, not E, for items to allow forgetting</em>
<a class="jxr_linenumber" name="429" href="#429">429</a> <em class="jxr_javadoccomment">     * them after use.  Relies heavily on Unsafe mechanics to minimize</em>
<a class="jxr_linenumber" name="430" href="#430">430</a> <em class="jxr_javadoccomment">     * unnecessary ordering constraints: Writes that are intrinsically</em>
<a class="jxr_linenumber" name="431" href="#431">431</a> <em class="jxr_javadoccomment">     * ordered wrt other accesses or CASes use simple relaxed forms.</em>
<a class="jxr_linenumber" name="432" href="#432">432</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="433" href="#433">433</a>     <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">class</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> {
<a class="jxr_linenumber" name="434" href="#434">434</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> isData;   <em class="jxr_comment">// false if this is a request node</em>
<a class="jxr_linenumber" name="435" href="#435">435</a>         <strong class="jxr_keyword">volatile</strong> Object item;   <em class="jxr_comment">// initially non-null if isData; CASed to match</em>
<a class="jxr_linenumber" name="436" href="#436">436</a>         <strong class="jxr_keyword">volatile</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> next;
<a class="jxr_linenumber" name="437" href="#437">437</a>         <strong class="jxr_keyword">volatile</strong> Thread waiter; <em class="jxr_comment">// null until waiting</em>
<a class="jxr_linenumber" name="438" href="#438">438</a> 
<a class="jxr_linenumber" name="439" href="#439">439</a>         <em class="jxr_comment">// CAS methods for fields</em>
<a class="jxr_linenumber" name="440" href="#440">440</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> casNext(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> cmp, <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> val) {
<a class="jxr_linenumber" name="441" href="#441">441</a>             <strong class="jxr_keyword">if</strong> (AtomicFieldUpdaterUtil.isAvailable()) {
<a class="jxr_linenumber" name="442" href="#442">442</a>                 <strong class="jxr_keyword">return</strong> nextUpdater.compareAndSet(<strong class="jxr_keyword">this</strong>, cmp, val);
<a class="jxr_linenumber" name="443" href="#443">443</a>             } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="444" href="#444">444</a>                 <strong class="jxr_keyword">synchronized</strong> (<strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="445" href="#445">445</a>                     <strong class="jxr_keyword">if</strong> (next == cmp) {
<a class="jxr_linenumber" name="446" href="#446">446</a>                         next = val;
<a class="jxr_linenumber" name="447" href="#447">447</a>                         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="448" href="#448">448</a>                     } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="449" href="#449">449</a>                         <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="450" href="#450">450</a>                     }
<a class="jxr_linenumber" name="451" href="#451">451</a>                 }
<a class="jxr_linenumber" name="452" href="#452">452</a>             }
<a class="jxr_linenumber" name="453" href="#453">453</a>         }
<a class="jxr_linenumber" name="454" href="#454">454</a> 
<a class="jxr_linenumber" name="455" href="#455">455</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> casItem(Object cmp, Object val) {
<a class="jxr_linenumber" name="456" href="#456">456</a>             <em class="jxr_comment">// assert cmp == null || cmp.getClass() != Node.class;</em>
<a class="jxr_linenumber" name="457" href="#457">457</a>             <strong class="jxr_keyword">if</strong> (AtomicFieldUpdaterUtil.isAvailable()) {
<a class="jxr_linenumber" name="458" href="#458">458</a>                 <strong class="jxr_keyword">return</strong> itemUpdater.compareAndSet(<strong class="jxr_keyword">this</strong>, cmp, val);
<a class="jxr_linenumber" name="459" href="#459">459</a>             } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="460" href="#460">460</a>                 <strong class="jxr_keyword">synchronized</strong> (<strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="461" href="#461">461</a>                     <strong class="jxr_keyword">if</strong> (item == cmp) {
<a class="jxr_linenumber" name="462" href="#462">462</a>                         item = val;
<a class="jxr_linenumber" name="463" href="#463">463</a>                         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="464" href="#464">464</a>                     } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="465" href="#465">465</a>                         <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="466" href="#466">466</a>                     }
<a class="jxr_linenumber" name="467" href="#467">467</a>                 }
<a class="jxr_linenumber" name="468" href="#468">468</a>             }
<a class="jxr_linenumber" name="469" href="#469">469</a>         }
<a class="jxr_linenumber" name="470" href="#470">470</a> 
<a class="jxr_linenumber" name="471" href="#471">471</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="472" href="#472">472</a> <em class="jxr_javadoccomment">         * Constructs a new node.  Uses relaxed write because item can</em>
<a class="jxr_linenumber" name="473" href="#473">473</a> <em class="jxr_javadoccomment">         * only be seen after publication via casNext.</em>
<a class="jxr_linenumber" name="474" href="#474">474</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="475" href="#475">475</a>         <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a>(Object item, <strong class="jxr_keyword">boolean</strong> isData) {
<a class="jxr_linenumber" name="476" href="#476">476</a>             <strong class="jxr_keyword">this</strong>.item = item;
<a class="jxr_linenumber" name="477" href="#477">477</a>             <strong class="jxr_keyword">this</strong>.isData = isData;
<a class="jxr_linenumber" name="478" href="#478">478</a>         }
<a class="jxr_linenumber" name="479" href="#479">479</a> 
<a class="jxr_linenumber" name="480" href="#480">480</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="481" href="#481">481</a> <em class="jxr_javadoccomment">         * Links node to itself to avoid garbage retention.  Called</em>
<a class="jxr_linenumber" name="482" href="#482">482</a> <em class="jxr_javadoccomment">         * only after CASing head field, so uses relaxed write.</em>
<a class="jxr_linenumber" name="483" href="#483">483</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="484" href="#484">484</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">void</strong> forgetNext() {
<a class="jxr_linenumber" name="485" href="#485">485</a>             <strong class="jxr_keyword">this</strong>.next = <strong class="jxr_keyword">this</strong>;
<a class="jxr_linenumber" name="486" href="#486">486</a>         }
<a class="jxr_linenumber" name="487" href="#487">487</a> 
<a class="jxr_linenumber" name="488" href="#488">488</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="489" href="#489">489</a> <em class="jxr_javadoccomment">         * Sets item to self and waiter to null, to avoid garbage</em>
<a class="jxr_linenumber" name="490" href="#490">490</a> <em class="jxr_javadoccomment">         * retention after matching or cancelling. Uses relaxed writes</em>
<a class="jxr_linenumber" name="491" href="#491">491</a> <em class="jxr_javadoccomment">         * bacause order is already constrained in the only calling</em>
<a class="jxr_linenumber" name="492" href="#492">492</a> <em class="jxr_javadoccomment">         * contexts: item is forgotten only after volatile/atomic</em>
<a class="jxr_linenumber" name="493" href="#493">493</a> <em class="jxr_javadoccomment">         * mechanics that extract items.  Similarly, clearing waiter</em>
<a class="jxr_linenumber" name="494" href="#494">494</a> <em class="jxr_javadoccomment">         * follows either CAS or return from park (if ever parked;</em>
<a class="jxr_linenumber" name="495" href="#495">495</a> <em class="jxr_javadoccomment">         * else we don't care).</em>
<a class="jxr_linenumber" name="496" href="#496">496</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="497" href="#497">497</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">void</strong> forgetContents() {
<a class="jxr_linenumber" name="498" href="#498">498</a>             <strong class="jxr_keyword">this</strong>.item = <strong class="jxr_keyword">this</strong>;
<a class="jxr_linenumber" name="499" href="#499">499</a>             <strong class="jxr_keyword">this</strong>.waiter = <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="500" href="#500">500</a>         }
<a class="jxr_linenumber" name="501" href="#501">501</a> 
<a class="jxr_linenumber" name="502" href="#502">502</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="503" href="#503">503</a> <em class="jxr_javadoccomment">         * Returns true if this node has been matched, including the</em>
<a class="jxr_linenumber" name="504" href="#504">504</a> <em class="jxr_javadoccomment">         * case of artificial matches due to cancellation.</em>
<a class="jxr_linenumber" name="505" href="#505">505</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="506" href="#506">506</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> isMatched() {
<a class="jxr_linenumber" name="507" href="#507">507</a>             Object x = item;
<a class="jxr_linenumber" name="508" href="#508">508</a>             <strong class="jxr_keyword">return</strong> x == <strong class="jxr_keyword">this</strong> || x == <strong class="jxr_keyword">null</strong> == isData;
<a class="jxr_linenumber" name="509" href="#509">509</a>         }
<a class="jxr_linenumber" name="510" href="#510">510</a> 
<a class="jxr_linenumber" name="511" href="#511">511</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="512" href="#512">512</a> <em class="jxr_javadoccomment">         * Returns true if this is an unmatched request node.</em>
<a class="jxr_linenumber" name="513" href="#513">513</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="514" href="#514">514</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> isUnmatchedRequest() {
<a class="jxr_linenumber" name="515" href="#515">515</a>             <strong class="jxr_keyword">return</strong> !isData &amp;&amp; item == <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="516" href="#516">516</a>         }
<a class="jxr_linenumber" name="517" href="#517">517</a> 
<a class="jxr_linenumber" name="518" href="#518">518</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="519" href="#519">519</a> <em class="jxr_javadoccomment">         * Returns true if a node with the given mode cannot be</em>
<a class="jxr_linenumber" name="520" href="#520">520</a> <em class="jxr_javadoccomment">         * appended to this node because this node is unmatched and</em>
<a class="jxr_linenumber" name="521" href="#521">521</a> <em class="jxr_javadoccomment">         * has opposite data mode.</em>
<a class="jxr_linenumber" name="522" href="#522">522</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="523" href="#523">523</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> cannotPrecede(<strong class="jxr_keyword">boolean</strong> haveData) {
<a class="jxr_linenumber" name="524" href="#524">524</a>             <strong class="jxr_keyword">boolean</strong> d = isData;
<a class="jxr_linenumber" name="525" href="#525">525</a>             Object x;
<a class="jxr_linenumber" name="526" href="#526">526</a>             <strong class="jxr_keyword">return</strong> d != haveData &amp;&amp; (x = item) != <strong class="jxr_keyword">this</strong> &amp;&amp; x != <strong class="jxr_keyword">null</strong> == d;
<a class="jxr_linenumber" name="527" href="#527">527</a>         }
<a class="jxr_linenumber" name="528" href="#528">528</a> 
<a class="jxr_linenumber" name="529" href="#529">529</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="530" href="#530">530</a> <em class="jxr_javadoccomment">         * Tries to artificially match a data node -- used by remove.</em>
<a class="jxr_linenumber" name="531" href="#531">531</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="532" href="#532">532</a>         <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> tryMatchData() {
<a class="jxr_linenumber" name="533" href="#533">533</a>             <em class="jxr_comment">// assert isData;</em>
<a class="jxr_linenumber" name="534" href="#534">534</a>             Object x = item;
<a class="jxr_linenumber" name="535" href="#535">535</a>             <strong class="jxr_keyword">if</strong> (x != <strong class="jxr_keyword">null</strong> &amp;&amp; x != <strong class="jxr_keyword">this</strong> &amp;&amp; casItem(x, <strong class="jxr_keyword">null</strong>)) {
<a class="jxr_linenumber" name="536" href="#536">536</a>                 LockSupport.unpark(waiter);
<a class="jxr_linenumber" name="537" href="#537">537</a>                 <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="538" href="#538">538</a>             }
<a class="jxr_linenumber" name="539" href="#539">539</a>             <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="540" href="#540">540</a>         }
<a class="jxr_linenumber" name="541" href="#541">541</a> 
<a class="jxr_linenumber" name="542" href="#542">542</a>         <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> AtomicReferenceFieldUpdater&lt;Node, Node&gt; nextUpdater =
<a class="jxr_linenumber" name="543" href="#543">543</a>             AtomicFieldUpdaterUtil.newRefUpdater(Node.<strong class="jxr_keyword">class</strong>, Node.<strong class="jxr_keyword">class</strong>, <span class="jxr_string">"next"</span>);
<a class="jxr_linenumber" name="544" href="#544">544</a>         <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> AtomicReferenceFieldUpdater&lt;Node, Object&gt; itemUpdater =
<a class="jxr_linenumber" name="545" href="#545">545</a>             AtomicFieldUpdaterUtil.newRefUpdater(Node.<strong class="jxr_keyword">class</strong>, Object.<strong class="jxr_keyword">class</strong>, <span class="jxr_string">"item"</span>);
<a class="jxr_linenumber" name="546" href="#546">546</a> 
<a class="jxr_linenumber" name="547" href="#547">547</a>         <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">long</strong> serialVersionUID = -3375979862319811754L;
<a class="jxr_linenumber" name="548" href="#548">548</a>     }
<a class="jxr_linenumber" name="549" href="#549">549</a> 
<a class="jxr_linenumber" name="550" href="#550">550</a>     <em class="jxr_javadoccomment">/**</em><em class="jxr_javadoccomment"> head of the queue; null until first enqueue */</em>
<a class="jxr_linenumber" name="551" href="#551">551</a>     <strong class="jxr_keyword">transient</strong> <strong class="jxr_keyword">volatile</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> head;
<a class="jxr_linenumber" name="552" href="#552">552</a> 
<a class="jxr_linenumber" name="553" href="#553">553</a>     <em class="jxr_javadoccomment">/**</em><em class="jxr_javadoccomment"> tail of the queue; null until first append */</em>
<a class="jxr_linenumber" name="554" href="#554">554</a>     <strong class="jxr_keyword">transient</strong> <strong class="jxr_keyword">volatile</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> tail;
<a class="jxr_linenumber" name="555" href="#555">555</a> 
<a class="jxr_linenumber" name="556" href="#556">556</a>     <em class="jxr_javadoccomment">/**</em><em class="jxr_javadoccomment"> The number of apparent failures to unsplice removed nodes */</em>
<a class="jxr_linenumber" name="557" href="#557">557</a>     <strong class="jxr_keyword">transient</strong> <strong class="jxr_keyword">volatile</strong> <strong class="jxr_keyword">int</strong> sweepVotes;
<a class="jxr_linenumber" name="558" href="#558">558</a> 
<a class="jxr_linenumber" name="559" href="#559">559</a>     <em class="jxr_comment">// CAS methods for fields</em>
<a class="jxr_linenumber" name="560" href="#560">560</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">boolean</strong> casTail(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> cmp, <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> val) {
<a class="jxr_linenumber" name="561" href="#561">561</a>         <strong class="jxr_keyword">if</strong> (AtomicFieldUpdaterUtil.isAvailable()) {
<a class="jxr_linenumber" name="562" href="#562">562</a>             <strong class="jxr_keyword">return</strong> tailUpdater.compareAndSet(<strong class="jxr_keyword">this</strong>, cmp, val);
<a class="jxr_linenumber" name="563" href="#563">563</a>         } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="564" href="#564">564</a>             <strong class="jxr_keyword">synchronized</strong> (<strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="565" href="#565">565</a>                 <strong class="jxr_keyword">if</strong> (tail == cmp) {
<a class="jxr_linenumber" name="566" href="#566">566</a>                     tail = val;
<a class="jxr_linenumber" name="567" href="#567">567</a>                     <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="568" href="#568">568</a>                 } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="569" href="#569">569</a>                     <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="570" href="#570">570</a>                 }
<a class="jxr_linenumber" name="571" href="#571">571</a>             }
<a class="jxr_linenumber" name="572" href="#572">572</a>         }
<a class="jxr_linenumber" name="573" href="#573">573</a>     }
<a class="jxr_linenumber" name="574" href="#574">574</a> 
<a class="jxr_linenumber" name="575" href="#575">575</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">boolean</strong> casHead(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> cmp, <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> val) {
<a class="jxr_linenumber" name="576" href="#576">576</a>         <strong class="jxr_keyword">if</strong> (AtomicFieldUpdaterUtil.isAvailable()) {
<a class="jxr_linenumber" name="577" href="#577">577</a>             <strong class="jxr_keyword">return</strong> headUpdater.compareAndSet(<strong class="jxr_keyword">this</strong>, cmp, val);
<a class="jxr_linenumber" name="578" href="#578">578</a>         } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="579" href="#579">579</a>             <strong class="jxr_keyword">synchronized</strong> (<strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="580" href="#580">580</a>                 <strong class="jxr_keyword">if</strong> (head == cmp) {
<a class="jxr_linenumber" name="581" href="#581">581</a>                     head = val;
<a class="jxr_linenumber" name="582" href="#582">582</a>                     <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="583" href="#583">583</a>                 } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="584" href="#584">584</a>                     <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="585" href="#585">585</a>                 }
<a class="jxr_linenumber" name="586" href="#586">586</a>             }
<a class="jxr_linenumber" name="587" href="#587">587</a>         }
<a class="jxr_linenumber" name="588" href="#588">588</a>     }
<a class="jxr_linenumber" name="589" href="#589">589</a> 
<a class="jxr_linenumber" name="590" href="#590">590</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">boolean</strong> casSweepVotes(<strong class="jxr_keyword">int</strong> cmp, <strong class="jxr_keyword">int</strong> val) {
<a class="jxr_linenumber" name="591" href="#591">591</a>         <strong class="jxr_keyword">if</strong> (AtomicFieldUpdaterUtil.isAvailable()) {
<a class="jxr_linenumber" name="592" href="#592">592</a>             <strong class="jxr_keyword">return</strong> sweepVotesUpdater.compareAndSet(<strong class="jxr_keyword">this</strong>, cmp, val);
<a class="jxr_linenumber" name="593" href="#593">593</a>         } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="594" href="#594">594</a>             <strong class="jxr_keyword">synchronized</strong> (<strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="595" href="#595">595</a>                 <strong class="jxr_keyword">if</strong> (sweepVotes == cmp) {
<a class="jxr_linenumber" name="596" href="#596">596</a>                     sweepVotes = val;
<a class="jxr_linenumber" name="597" href="#597">597</a>                     <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="598" href="#598">598</a>                 } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="599" href="#599">599</a>                     <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="600" href="#600">600</a>                 }
<a class="jxr_linenumber" name="601" href="#601">601</a>             }
<a class="jxr_linenumber" name="602" href="#602">602</a>         }
<a class="jxr_linenumber" name="603" href="#603">603</a>     }
<a class="jxr_linenumber" name="604" href="#604">604</a> 
<a class="jxr_linenumber" name="605" href="#605">605</a>     <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="606" href="#606">606</a> <em class="jxr_comment">     * Possible values for "how" argument in xfer method.</em>
<a class="jxr_linenumber" name="607" href="#607">607</a> <em class="jxr_comment">     */</em>
<a class="jxr_linenumber" name="608" href="#608">608</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> NOW   = 0; <em class="jxr_comment">// for untimed poll, tryTransfer</em>
<a class="jxr_linenumber" name="609" href="#609">609</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> ASYNC = 1; <em class="jxr_comment">// for offer, put, add</em>
<a class="jxr_linenumber" name="610" href="#610">610</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> SYNC  = 2; <em class="jxr_comment">// for transfer, take</em>
<a class="jxr_linenumber" name="611" href="#611">611</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">int</strong> TIMED = 3; <em class="jxr_comment">// for timed poll, tryTransfer</em>
<a class="jxr_linenumber" name="612" href="#612">612</a> 
<a class="jxr_linenumber" name="613" href="#613">613</a>     @SuppressWarnings(<span class="jxr_string">"unchecked"</span>)
<a class="jxr_linenumber" name="614" href="#614">614</a>     <strong class="jxr_keyword">static</strong> &lt;E&gt; E <strong class="jxr_keyword">cast</strong>(Object item) {
<a class="jxr_linenumber" name="615" href="#615">615</a>         <em class="jxr_comment">// assert item == null || item.getClass() != Node.class;</em>
<a class="jxr_linenumber" name="616" href="#616">616</a>         <strong class="jxr_keyword">return</strong> (E) item;
<a class="jxr_linenumber" name="617" href="#617">617</a>     }
<a class="jxr_linenumber" name="618" href="#618">618</a> 
<a class="jxr_linenumber" name="619" href="#619">619</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="620" href="#620">620</a> <em class="jxr_javadoccomment">     * Implements all queuing methods. See above for explanation.</em>
<a class="jxr_linenumber" name="621" href="#621">621</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="622" href="#622">622</a> <em class="jxr_javadoccomment">     * @param e the item or null for take</em>
<a class="jxr_linenumber" name="623" href="#623">623</a> <em class="jxr_javadoccomment">     * @param haveData true if this is a put, else a take</em>
<a class="jxr_linenumber" name="624" href="#624">624</a> <em class="jxr_javadoccomment">     * @param how NOW, ASYNC, SYNC, or TIMED</em>
<a class="jxr_linenumber" name="625" href="#625">625</a> <em class="jxr_javadoccomment">     * @param nanos timeout in nanosecs, used only if mode is TIMED</em>
<a class="jxr_linenumber" name="626" href="#626">626</a> <em class="jxr_javadoccomment">     * @return an item if matched, else e</em>
<a class="jxr_linenumber" name="627" href="#627">627</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if haveData mode but e is null</em>
<a class="jxr_linenumber" name="628" href="#628">628</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="629" href="#629">629</a>     <strong class="jxr_keyword">private</strong> E xfer(E e, <strong class="jxr_keyword">boolean</strong> haveData, <strong class="jxr_keyword">int</strong> how, <strong class="jxr_keyword">long</strong> nanos) {
<a class="jxr_linenumber" name="630" href="#630">630</a>         <strong class="jxr_keyword">if</strong> (haveData &amp;&amp; e == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="631" href="#631">631</a>             <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> NullPointerException();
<a class="jxr_linenumber" name="632" href="#632">632</a>         }
<a class="jxr_linenumber" name="633" href="#633">633</a>         <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> s = <strong class="jxr_keyword">null</strong>;                        <em class="jxr_comment">// the node to append, if needed</em>
<a class="jxr_linenumber" name="634" href="#634">634</a> 
<a class="jxr_linenumber" name="635" href="#635">635</a>         retry: <strong class="jxr_keyword">for</strong> (;;) {                     <em class="jxr_comment">// restart on append race</em>
<a class="jxr_linenumber" name="636" href="#636">636</a> 
<a class="jxr_linenumber" name="637" href="#637">637</a>             <strong class="jxr_keyword">for</strong> (Node h = head, p = h; p != <strong class="jxr_keyword">null</strong>;) { <em class="jxr_comment">// find &amp; match first node</em>
<a class="jxr_linenumber" name="638" href="#638">638</a>                 <strong class="jxr_keyword">boolean</strong> isData = p.isData;
<a class="jxr_linenumber" name="639" href="#639">639</a>                 Object item = p.item;
<a class="jxr_linenumber" name="640" href="#640">640</a>                 <strong class="jxr_keyword">if</strong> (item != p &amp;&amp; item != <strong class="jxr_keyword">null</strong> == isData) { <em class="jxr_comment">// unmatched</em>
<a class="jxr_linenumber" name="641" href="#641">641</a>                     <strong class="jxr_keyword">if</strong> (isData == haveData) { <em class="jxr_comment">// can't match</em>
<a class="jxr_linenumber" name="642" href="#642">642</a>                         <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="643" href="#643">643</a>                     }
<a class="jxr_linenumber" name="644" href="#644">644</a>                     <strong class="jxr_keyword">if</strong> (p.casItem(item, e)) { <em class="jxr_comment">// match</em>
<a class="jxr_linenumber" name="645" href="#645">645</a>                         <strong class="jxr_keyword">for</strong> (Node q = p; q != h;) {
<a class="jxr_linenumber" name="646" href="#646">646</a>                             <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> n = q.next;  <em class="jxr_comment">// update by 2 unless singleton</em>
<a class="jxr_linenumber" name="647" href="#647">647</a>                             <strong class="jxr_keyword">if</strong> (head == h &amp;&amp; casHead(h, n == <strong class="jxr_keyword">null</strong>? q : n)) {
<a class="jxr_linenumber" name="648" href="#648">648</a>                                 h.forgetNext();
<a class="jxr_linenumber" name="649" href="#649">649</a>                                 <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="650" href="#650">650</a>                             }                 <em class="jxr_comment">// advance and retry</em>
<a class="jxr_linenumber" name="651" href="#651">651</a>                             <strong class="jxr_keyword">if</strong> ((h = head)   == <strong class="jxr_keyword">null</strong> ||
<a class="jxr_linenumber" name="652" href="#652">652</a>                                 (q = h.next) == <strong class="jxr_keyword">null</strong> || !q.isMatched()) {
<a class="jxr_linenumber" name="653" href="#653">653</a>                                 <strong class="jxr_keyword">break</strong>;        <em class="jxr_comment">// unless slack &lt; 2</em>
<a class="jxr_linenumber" name="654" href="#654">654</a>                             }
<a class="jxr_linenumber" name="655" href="#655">655</a>                         }
<a class="jxr_linenumber" name="656" href="#656">656</a>                         LockSupport.unpark(p.waiter);
<a class="jxr_linenumber" name="657" href="#657">657</a>                         <strong class="jxr_keyword">return</strong> LinkedTransferQueue.&lt;E&gt;<strong class="jxr_keyword">cast</strong>(item);
<a class="jxr_linenumber" name="658" href="#658">658</a>                     }
<a class="jxr_linenumber" name="659" href="#659">659</a>                 }
<a class="jxr_linenumber" name="660" href="#660">660</a>                 <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> n = p.next;
<a class="jxr_linenumber" name="661" href="#661">661</a>                 p = p != n ? n : (h = head); <em class="jxr_comment">// Use head if p offlist</em>
<a class="jxr_linenumber" name="662" href="#662">662</a>             }
<a class="jxr_linenumber" name="663" href="#663">663</a> 
<a class="jxr_linenumber" name="664" href="#664">664</a>             <strong class="jxr_keyword">if</strong> (how != NOW) {                 <em class="jxr_comment">// No matches available</em>
<a class="jxr_linenumber" name="665" href="#665">665</a>                 <strong class="jxr_keyword">if</strong> (s == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="666" href="#666">666</a>                     s = <strong class="jxr_keyword">new</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a>(e, haveData);
<a class="jxr_linenumber" name="667" href="#667">667</a>                 }
<a class="jxr_linenumber" name="668" href="#668">668</a>                 <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> pred = tryAppend(s, haveData);
<a class="jxr_linenumber" name="669" href="#669">669</a>                 <strong class="jxr_keyword">if</strong> (pred == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="670" href="#670">670</a>                     <strong class="jxr_keyword">continue</strong> retry;           <em class="jxr_comment">// lost race vs opposite mode</em>
<a class="jxr_linenumber" name="671" href="#671">671</a>                 }
<a class="jxr_linenumber" name="672" href="#672">672</a>                 <strong class="jxr_keyword">if</strong> (how != ASYNC) {
<a class="jxr_linenumber" name="673" href="#673">673</a>                     <strong class="jxr_keyword">return</strong> awaitMatch(s, pred, e, (how == TIMED), nanos);
<a class="jxr_linenumber" name="674" href="#674">674</a>                 }
<a class="jxr_linenumber" name="675" href="#675">675</a>             }
<a class="jxr_linenumber" name="676" href="#676">676</a>             <strong class="jxr_keyword">return</strong> e; <em class="jxr_comment">// not waiting</em>
<a class="jxr_linenumber" name="677" href="#677">677</a>         }
<a class="jxr_linenumber" name="678" href="#678">678</a>     }
<a class="jxr_linenumber" name="679" href="#679">679</a> 
<a class="jxr_linenumber" name="680" href="#680">680</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="681" href="#681">681</a> <em class="jxr_javadoccomment">     * Tries to append node s as tail.</em>
<a class="jxr_linenumber" name="682" href="#682">682</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="683" href="#683">683</a> <em class="jxr_javadoccomment">     * @param s the node to append</em>
<a class="jxr_linenumber" name="684" href="#684">684</a> <em class="jxr_javadoccomment">     * @param haveData true if appending in data mode</em>
<a class="jxr_linenumber" name="685" href="#685">685</a> <em class="jxr_javadoccomment">     * @return null on failure due to losing race with append in</em>
<a class="jxr_linenumber" name="686" href="#686">686</a> <em class="jxr_javadoccomment">     * different mode, else s's predecessor, or s itself if no</em>
<a class="jxr_linenumber" name="687" href="#687">687</a> <em class="jxr_javadoccomment">     * predecessor</em>
<a class="jxr_linenumber" name="688" href="#688">688</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="689" href="#689">689</a>     <strong class="jxr_keyword">private</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> tryAppend(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> s, <strong class="jxr_keyword">boolean</strong> haveData) {
<a class="jxr_linenumber" name="690" href="#690">690</a>         <strong class="jxr_keyword">for</strong> (Node t = tail, p = t;;) {        <em class="jxr_comment">// move p to last node and append</em>
<a class="jxr_linenumber" name="691" href="#691">691</a>             <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> n, u;                        <em class="jxr_comment">// temps for reads of next &amp; tail</em>
<a class="jxr_linenumber" name="692" href="#692">692</a>             <strong class="jxr_keyword">if</strong> (p == <strong class="jxr_keyword">null</strong> &amp;&amp; (p = head) == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="693" href="#693">693</a>                 <strong class="jxr_keyword">if</strong> (casHead(<strong class="jxr_keyword">null</strong>, s)) {
<a class="jxr_linenumber" name="694" href="#694">694</a>                     <strong class="jxr_keyword">return</strong> s;                 <em class="jxr_comment">// initialize</em>
<a class="jxr_linenumber" name="695" href="#695">695</a>                 }
<a class="jxr_linenumber" name="696" href="#696">696</a>             }
<a class="jxr_linenumber" name="697" href="#697">697</a>             <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (p.cannotPrecede(haveData)) {
<a class="jxr_linenumber" name="698" href="#698">698</a>                 <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">null</strong>;                  <em class="jxr_comment">// lost race vs opposite mode</em>
<a class="jxr_linenumber" name="699" href="#699">699</a>             } <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> ((n = p.next) != <strong class="jxr_keyword">null</strong>) { <em class="jxr_comment">// not last; keep traversing</em>
<a class="jxr_linenumber" name="700" href="#700">700</a>                 p = p != t &amp;&amp; t != (u = tail) ? (t = u) : <em class="jxr_comment">// stale tail</em>
<a class="jxr_linenumber" name="701" href="#701">701</a>                     p != n ? n : <strong class="jxr_keyword">null</strong>;      <em class="jxr_comment">// restart if off list</em>
<a class="jxr_linenumber" name="702" href="#702">702</a>             } <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (!p.casNext(<strong class="jxr_keyword">null</strong>, s)) {
<a class="jxr_linenumber" name="703" href="#703">703</a>                 p = p.next;                   <em class="jxr_comment">// re-read on CAS failure</em>
<a class="jxr_linenumber" name="704" href="#704">704</a>             } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="705" href="#705">705</a>                 <strong class="jxr_keyword">if</strong> (p != t) {                 <em class="jxr_comment">// update if slack now &gt;= 2</em>
<a class="jxr_linenumber" name="706" href="#706">706</a>                     <strong class="jxr_keyword">while</strong> ((tail != t || !casTail(t, s)) &amp;&amp;
<a class="jxr_linenumber" name="707" href="#707">707</a>                            (t = tail)   != <strong class="jxr_keyword">null</strong> &amp;&amp;
<a class="jxr_linenumber" name="708" href="#708">708</a>                            (s = t.next) != <strong class="jxr_keyword">null</strong> &amp;&amp; <em class="jxr_comment">// advance and retry</em>
<a class="jxr_linenumber" name="709" href="#709">709</a>                            (s = s.next) != <strong class="jxr_keyword">null</strong> &amp;&amp; s != t) {
<a class="jxr_linenumber" name="710" href="#710">710</a>                         <strong class="jxr_keyword">continue</strong>;
<a class="jxr_linenumber" name="711" href="#711">711</a>                     }
<a class="jxr_linenumber" name="712" href="#712">712</a>                 }
<a class="jxr_linenumber" name="713" href="#713">713</a>                 <strong class="jxr_keyword">return</strong> p;
<a class="jxr_linenumber" name="714" href="#714">714</a>             }
<a class="jxr_linenumber" name="715" href="#715">715</a>         }
<a class="jxr_linenumber" name="716" href="#716">716</a>     }
<a class="jxr_linenumber" name="717" href="#717">717</a> 
<a class="jxr_linenumber" name="718" href="#718">718</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="719" href="#719">719</a> <em class="jxr_javadoccomment">     * Spins/yields/blocks until node s is matched or caller gives up.</em>
<a class="jxr_linenumber" name="720" href="#720">720</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="721" href="#721">721</a> <em class="jxr_javadoccomment">     * @param s the waiting node</em>
<a class="jxr_linenumber" name="722" href="#722">722</a> <em class="jxr_javadoccomment">     * @param pred the predecessor of s, or s itself if it has no</em>
<a class="jxr_linenumber" name="723" href="#723">723</a> <em class="jxr_javadoccomment">     * predecessor, or null if unknown (the null case does not occur</em>
<a class="jxr_linenumber" name="724" href="#724">724</a> <em class="jxr_javadoccomment">     * in any current calls but may in possible future extensions)</em>
<a class="jxr_linenumber" name="725" href="#725">725</a> <em class="jxr_javadoccomment">     * @param e the comparison value for checking match</em>
<a class="jxr_linenumber" name="726" href="#726">726</a> <em class="jxr_javadoccomment">     * @param timed if true, wait only until timeout elapses</em>
<a class="jxr_linenumber" name="727" href="#727">727</a> <em class="jxr_javadoccomment">     * @param nanos timeout in nanosecs, used only if timed is true</em>
<a class="jxr_linenumber" name="728" href="#728">728</a> <em class="jxr_javadoccomment">     * @return matched item, or e if unmatched on interrupt or timeout</em>
<a class="jxr_linenumber" name="729" href="#729">729</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="730" href="#730">730</a>     <strong class="jxr_keyword">private</strong> E awaitMatch(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> s, <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> pred, E e, <strong class="jxr_keyword">boolean</strong> timed, <strong class="jxr_keyword">long</strong> nanos) {
<a class="jxr_linenumber" name="731" href="#731">731</a>         <strong class="jxr_keyword">long</strong> lastTime = timed ? System.nanoTime() : 0L;
<a class="jxr_linenumber" name="732" href="#732">732</a>         Thread w = Thread.currentThread();
<a class="jxr_linenumber" name="733" href="#733">733</a>         <strong class="jxr_keyword">int</strong> spins = -1; <em class="jxr_comment">// initialized after first item and cancel checks</em>
<a class="jxr_linenumber" name="734" href="#734">734</a>         <a href="../../../../../org/jboss/netty/util/internal/ThreadLocalRandom.html">ThreadLocalRandom</a> randomYields = <strong class="jxr_keyword">null</strong>; <em class="jxr_comment">// bound if needed</em>
<a class="jxr_linenumber" name="735" href="#735">735</a> 
<a class="jxr_linenumber" name="736" href="#736">736</a>         <strong class="jxr_keyword">for</strong> (;;) {
<a class="jxr_linenumber" name="737" href="#737">737</a>             Object item = s.item;
<a class="jxr_linenumber" name="738" href="#738">738</a>             <strong class="jxr_keyword">if</strong> (item != e) {                  <em class="jxr_comment">// matched</em>
<a class="jxr_linenumber" name="739" href="#739">739</a>                 <em class="jxr_comment">// assert item != s;</em>
<a class="jxr_linenumber" name="740" href="#740">740</a>                 s.forgetContents();           <em class="jxr_comment">// avoid garbage</em>
<a class="jxr_linenumber" name="741" href="#741">741</a>                 <strong class="jxr_keyword">return</strong> LinkedTransferQueue.&lt;E&gt;<strong class="jxr_keyword">cast</strong>(item);
<a class="jxr_linenumber" name="742" href="#742">742</a>             }
<a class="jxr_linenumber" name="743" href="#743">743</a>             <strong class="jxr_keyword">if</strong> ((w.isInterrupted() || timed &amp;&amp; nanos &lt;= 0) &amp;&amp;
<a class="jxr_linenumber" name="744" href="#744">744</a>                     s.casItem(e, s)) {        <em class="jxr_comment">// cancel</em>
<a class="jxr_linenumber" name="745" href="#745">745</a>                 unsplice(pred, s);
<a class="jxr_linenumber" name="746" href="#746">746</a>                 <strong class="jxr_keyword">return</strong> e;
<a class="jxr_linenumber" name="747" href="#747">747</a>             }
<a class="jxr_linenumber" name="748" href="#748">748</a> 
<a class="jxr_linenumber" name="749" href="#749">749</a>             <strong class="jxr_keyword">if</strong> (spins &lt; 0) {                  <em class="jxr_comment">// establish spins at/near front</em>
<a class="jxr_linenumber" name="750" href="#750">750</a>                 <strong class="jxr_keyword">if</strong> ((spins = spinsFor(pred, s.isData)) &gt; 0) {
<a class="jxr_linenumber" name="751" href="#751">751</a>                     randomYields = ThreadLocalRandom.current();
<a class="jxr_linenumber" name="752" href="#752">752</a>                 }
<a class="jxr_linenumber" name="753" href="#753">753</a>             }
<a class="jxr_linenumber" name="754" href="#754">754</a>             <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (spins &gt; 0) {             <em class="jxr_comment">// spin</em>
<a class="jxr_linenumber" name="755" href="#755">755</a>                 --spins;
<a class="jxr_linenumber" name="756" href="#756">756</a>                 <strong class="jxr_keyword">if</strong> (randomYields.nextInt(CHAINED_SPINS) == 0) {
<a class="jxr_linenumber" name="757" href="#757">757</a>                     Thread.yield();           <em class="jxr_comment">// occasionally yield</em>
<a class="jxr_linenumber" name="758" href="#758">758</a>                 }
<a class="jxr_linenumber" name="759" href="#759">759</a>             }
<a class="jxr_linenumber" name="760" href="#760">760</a>             <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (s.waiter == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="761" href="#761">761</a>                 s.waiter = w;                 <em class="jxr_comment">// request unpark then recheck</em>
<a class="jxr_linenumber" name="762" href="#762">762</a>             }
<a class="jxr_linenumber" name="763" href="#763">763</a>             <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (timed) {
<a class="jxr_linenumber" name="764" href="#764">764</a>                 <strong class="jxr_keyword">long</strong> now = System.nanoTime();
<a class="jxr_linenumber" name="765" href="#765">765</a>                 <strong class="jxr_keyword">if</strong> ((nanos -= now - lastTime) &gt; 0) {
<a class="jxr_linenumber" name="766" href="#766">766</a>                     LockSupport.parkNanos(nanos);
<a class="jxr_linenumber" name="767" href="#767">767</a>                 }
<a class="jxr_linenumber" name="768" href="#768">768</a>                 lastTime = now;
<a class="jxr_linenumber" name="769" href="#769">769</a>             }
<a class="jxr_linenumber" name="770" href="#770">770</a>             <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="771" href="#771">771</a>                 LockSupport.park();
<a class="jxr_linenumber" name="772" href="#772">772</a>             }
<a class="jxr_linenumber" name="773" href="#773">773</a>         }
<a class="jxr_linenumber" name="774" href="#774">774</a>     }
<a class="jxr_linenumber" name="775" href="#775">775</a> 
<a class="jxr_linenumber" name="776" href="#776">776</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="777" href="#777">777</a> <em class="jxr_javadoccomment">     * Returns spin/yield value for a node with given predecessor and</em>
<a class="jxr_linenumber" name="778" href="#778">778</a> <em class="jxr_javadoccomment">     * data mode. See above for explanation.</em>
<a class="jxr_linenumber" name="779" href="#779">779</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="780" href="#780">780</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">int</strong> spinsFor(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> pred, <strong class="jxr_keyword">boolean</strong> haveData) {
<a class="jxr_linenumber" name="781" href="#781">781</a>         <strong class="jxr_keyword">if</strong> (MP &amp;&amp; pred != <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="782" href="#782">782</a>             <strong class="jxr_keyword">if</strong> (pred.isData != haveData) {    <em class="jxr_comment">// phase change</em>
<a class="jxr_linenumber" name="783" href="#783">783</a>                 <strong class="jxr_keyword">return</strong> FRONT_SPINS + CHAINED_SPINS;
<a class="jxr_linenumber" name="784" href="#784">784</a>             }
<a class="jxr_linenumber" name="785" href="#785">785</a>             <strong class="jxr_keyword">if</strong> (pred.isMatched()) {           <em class="jxr_comment">// probably at front</em>
<a class="jxr_linenumber" name="786" href="#786">786</a>                 <strong class="jxr_keyword">return</strong> FRONT_SPINS;
<a class="jxr_linenumber" name="787" href="#787">787</a>             }
<a class="jxr_linenumber" name="788" href="#788">788</a>             <strong class="jxr_keyword">if</strong> (pred.waiter == <strong class="jxr_keyword">null</strong>) {        <em class="jxr_comment">// pred apparently spinning</em>
<a class="jxr_linenumber" name="789" href="#789">789</a>                 <strong class="jxr_keyword">return</strong> CHAINED_SPINS;
<a class="jxr_linenumber" name="790" href="#790">790</a>             }
<a class="jxr_linenumber" name="791" href="#791">791</a>         }
<a class="jxr_linenumber" name="792" href="#792">792</a>         <strong class="jxr_keyword">return</strong> 0;
<a class="jxr_linenumber" name="793" href="#793">793</a>     }
<a class="jxr_linenumber" name="794" href="#794">794</a> 
<a class="jxr_linenumber" name="795" href="#795">795</a>     <em class="jxr_comment">/*<em class="jxr_comment"> -------------- Traversal methods -------------- */</em></em>
<a class="jxr_linenumber" name="796" href="#796">796</a> 
<a class="jxr_linenumber" name="797" href="#797">797</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="798" href="#798">798</a> <em class="jxr_javadoccomment">     * Returns the successor of p, or the head node if p.next has been</em>
<a class="jxr_linenumber" name="799" href="#799">799</a> <em class="jxr_javadoccomment">     * linked to self, which will only be true if traversing with a</em>
<a class="jxr_linenumber" name="800" href="#800">800</a> <em class="jxr_javadoccomment">     * stale pointer that is now off the list.</em>
<a class="jxr_linenumber" name="801" href="#801">801</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="802" href="#802">802</a>     <strong class="jxr_keyword">final</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> succ(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> p) {
<a class="jxr_linenumber" name="803" href="#803">803</a>         <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> next = p.next;
<a class="jxr_linenumber" name="804" href="#804">804</a>         <strong class="jxr_keyword">return</strong> p == next ? head : next;
<a class="jxr_linenumber" name="805" href="#805">805</a>     }
<a class="jxr_linenumber" name="806" href="#806">806</a> 
<a class="jxr_linenumber" name="807" href="#807">807</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="808" href="#808">808</a> <em class="jxr_javadoccomment">     * Returns the first unmatched node of the given mode, or null if</em>
<a class="jxr_linenumber" name="809" href="#809">809</a> <em class="jxr_javadoccomment">     * none.  Used by methods isEmpty, hasWaitingConsumer.</em>
<a class="jxr_linenumber" name="810" href="#810">810</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="811" href="#811">811</a>     <strong class="jxr_keyword">private</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> firstOfMode(<strong class="jxr_keyword">boolean</strong> isData) {
<a class="jxr_linenumber" name="812" href="#812">812</a>         <strong class="jxr_keyword">for</strong> (Node p = head; p != <strong class="jxr_keyword">null</strong>; p = succ(p)) {
<a class="jxr_linenumber" name="813" href="#813">813</a>             <strong class="jxr_keyword">if</strong> (!p.isMatched()) {
<a class="jxr_linenumber" name="814" href="#814">814</a>                 <strong class="jxr_keyword">return</strong> p.isData == isData ? p : <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="815" href="#815">815</a>             }
<a class="jxr_linenumber" name="816" href="#816">816</a>         }
<a class="jxr_linenumber" name="817" href="#817">817</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="818" href="#818">818</a>     }
<a class="jxr_linenumber" name="819" href="#819">819</a> 
<a class="jxr_linenumber" name="820" href="#820">820</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="821" href="#821">821</a> <em class="jxr_javadoccomment">     * Returns the item in the first unmatched node with isData; or</em>
<a class="jxr_linenumber" name="822" href="#822">822</a> <em class="jxr_javadoccomment">     * null if none.  Used by peek.</em>
<a class="jxr_linenumber" name="823" href="#823">823</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="824" href="#824">824</a>     <strong class="jxr_keyword">private</strong> E firstDataItem() {
<a class="jxr_linenumber" name="825" href="#825">825</a>         <strong class="jxr_keyword">for</strong> (Node p = head; p != <strong class="jxr_keyword">null</strong>; p = succ(p)) {
<a class="jxr_linenumber" name="826" href="#826">826</a>             Object item = p.item;
<a class="jxr_linenumber" name="827" href="#827">827</a>             <strong class="jxr_keyword">if</strong> (p.isData) {
<a class="jxr_linenumber" name="828" href="#828">828</a>                 <strong class="jxr_keyword">if</strong> (item != <strong class="jxr_keyword">null</strong> &amp;&amp; item != p) {
<a class="jxr_linenumber" name="829" href="#829">829</a>                     <strong class="jxr_keyword">return</strong> LinkedTransferQueue.&lt;E&gt;<strong class="jxr_keyword">cast</strong>(item);
<a class="jxr_linenumber" name="830" href="#830">830</a>                 }
<a class="jxr_linenumber" name="831" href="#831">831</a>             }
<a class="jxr_linenumber" name="832" href="#832">832</a>             <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (item == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="833" href="#833">833</a>                 <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="834" href="#834">834</a>             }
<a class="jxr_linenumber" name="835" href="#835">835</a>         }
<a class="jxr_linenumber" name="836" href="#836">836</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="837" href="#837">837</a>     }
<a class="jxr_linenumber" name="838" href="#838">838</a> 
<a class="jxr_linenumber" name="839" href="#839">839</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="840" href="#840">840</a> <em class="jxr_javadoccomment">     * Traverses and counts unmatched nodes of the given mode.</em>
<a class="jxr_linenumber" name="841" href="#841">841</a> <em class="jxr_javadoccomment">     * Used by methods size and getWaitingConsumerCount.</em>
<a class="jxr_linenumber" name="842" href="#842">842</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="843" href="#843">843</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">int</strong> countOfMode(<strong class="jxr_keyword">boolean</strong> data) {
<a class="jxr_linenumber" name="844" href="#844">844</a>         <strong class="jxr_keyword">int</strong> count = 0;
<a class="jxr_linenumber" name="845" href="#845">845</a>         <strong class="jxr_keyword">for</strong> (Node p = head; p != <strong class="jxr_keyword">null</strong>; ) {
<a class="jxr_linenumber" name="846" href="#846">846</a>             <strong class="jxr_keyword">if</strong> (!p.isMatched()) {
<a class="jxr_linenumber" name="847" href="#847">847</a>                 <strong class="jxr_keyword">if</strong> (p.isData != data) {
<a class="jxr_linenumber" name="848" href="#848">848</a>                     <strong class="jxr_keyword">return</strong> 0;
<a class="jxr_linenumber" name="849" href="#849">849</a>                 }
<a class="jxr_linenumber" name="850" href="#850">850</a>                 <strong class="jxr_keyword">if</strong> (++count == Integer.MAX_VALUE) { <em class="jxr_comment">// saturated</em>
<a class="jxr_linenumber" name="851" href="#851">851</a>                     <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="852" href="#852">852</a>                 }
<a class="jxr_linenumber" name="853" href="#853">853</a>             }
<a class="jxr_linenumber" name="854" href="#854">854</a>             <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> n = p.next;
<a class="jxr_linenumber" name="855" href="#855">855</a>             <strong class="jxr_keyword">if</strong> (n != p) {
<a class="jxr_linenumber" name="856" href="#856">856</a>                 p = n;
<a class="jxr_linenumber" name="857" href="#857">857</a>             } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="858" href="#858">858</a>                 count = 0;
<a class="jxr_linenumber" name="859" href="#859">859</a>                 p = head;
<a class="jxr_linenumber" name="860" href="#860">860</a>             }
<a class="jxr_linenumber" name="861" href="#861">861</a>         }
<a class="jxr_linenumber" name="862" href="#862">862</a>         <strong class="jxr_keyword">return</strong> count;
<a class="jxr_linenumber" name="863" href="#863">863</a>     }
<a class="jxr_linenumber" name="864" href="#864">864</a> 
<a class="jxr_linenumber" name="865" href="#865">865</a>     <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">class</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Itr</a> <strong class="jxr_keyword">implements</strong> Iterator&lt;E&gt; {
<a class="jxr_linenumber" name="866" href="#866">866</a>         <strong class="jxr_keyword">private</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> nextNode;   <em class="jxr_comment">// next node to return item for</em>
<a class="jxr_linenumber" name="867" href="#867">867</a>         <strong class="jxr_keyword">private</strong> E nextItem;      <em class="jxr_comment">// the corresponding item</em>
<a class="jxr_linenumber" name="868" href="#868">868</a>         <strong class="jxr_keyword">private</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> lastRet;    <em class="jxr_comment">// last returned node, to support remove</em>
<a class="jxr_linenumber" name="869" href="#869">869</a>         <strong class="jxr_keyword">private</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> lastPred;   <em class="jxr_comment">// predecessor to unlink lastRet</em>
<a class="jxr_linenumber" name="870" href="#870">870</a> 
<a class="jxr_linenumber" name="871" href="#871">871</a>         <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="872" href="#872">872</a> <em class="jxr_javadoccomment">         * Moves to next node after prev, or first node if prev null.</em>
<a class="jxr_linenumber" name="873" href="#873">873</a> <em class="jxr_javadoccomment">         */</em>
<a class="jxr_linenumber" name="874" href="#874">874</a>         <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">void</strong> advance(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> prev) {
<a class="jxr_linenumber" name="875" href="#875">875</a>             lastPred = lastRet;
<a class="jxr_linenumber" name="876" href="#876">876</a>             lastRet = prev;
<a class="jxr_linenumber" name="877" href="#877">877</a>             <strong class="jxr_keyword">for</strong> (Node p = prev == <strong class="jxr_keyword">null</strong> ? head : succ(prev);
<a class="jxr_linenumber" name="878" href="#878">878</a>                  p != <strong class="jxr_keyword">null</strong>; p = succ(p)) {
<a class="jxr_linenumber" name="879" href="#879">879</a>                 Object item = p.item;
<a class="jxr_linenumber" name="880" href="#880">880</a>                 <strong class="jxr_keyword">if</strong> (p.isData) {
<a class="jxr_linenumber" name="881" href="#881">881</a>                     <strong class="jxr_keyword">if</strong> (item != <strong class="jxr_keyword">null</strong> &amp;&amp; item != p) {
<a class="jxr_linenumber" name="882" href="#882">882</a>                         nextItem = LinkedTransferQueue.&lt;E&gt;<strong class="jxr_keyword">cast</strong>(item);
<a class="jxr_linenumber" name="883" href="#883">883</a>                         nextNode = p;
<a class="jxr_linenumber" name="884" href="#884">884</a>                         <strong class="jxr_keyword">return</strong>;
<a class="jxr_linenumber" name="885" href="#885">885</a>                     }
<a class="jxr_linenumber" name="886" href="#886">886</a>                 }
<a class="jxr_linenumber" name="887" href="#887">887</a>                 <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (item == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="888" href="#888">888</a>                     <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="889" href="#889">889</a>                 }
<a class="jxr_linenumber" name="890" href="#890">890</a>             }
<a class="jxr_linenumber" name="891" href="#891">891</a>             nextNode = <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="892" href="#892">892</a>         }
<a class="jxr_linenumber" name="893" href="#893">893</a> 
<a class="jxr_linenumber" name="894" href="#894">894</a>         <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Itr</a>() {
<a class="jxr_linenumber" name="895" href="#895">895</a>             advance(<strong class="jxr_keyword">null</strong>);
<a class="jxr_linenumber" name="896" href="#896">896</a>         }
<a class="jxr_linenumber" name="897" href="#897">897</a> 
<a class="jxr_linenumber" name="898" href="#898">898</a>         <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">boolean</strong> hasNext() {
<a class="jxr_linenumber" name="899" href="#899">899</a>             <strong class="jxr_keyword">return</strong> nextNode != <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="900" href="#900">900</a>         }
<a class="jxr_linenumber" name="901" href="#901">901</a> 
<a class="jxr_linenumber" name="902" href="#902">902</a>         <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">final</strong> E next() {
<a class="jxr_linenumber" name="903" href="#903">903</a>             <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> p = nextNode;
<a class="jxr_linenumber" name="904" href="#904">904</a>             <strong class="jxr_keyword">if</strong> (p == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="905" href="#905">905</a>                 <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> NoSuchElementException();
<a class="jxr_linenumber" name="906" href="#906">906</a>             }
<a class="jxr_linenumber" name="907" href="#907">907</a>             E e = nextItem;
<a class="jxr_linenumber" name="908" href="#908">908</a>             advance(p);
<a class="jxr_linenumber" name="909" href="#909">909</a>             <strong class="jxr_keyword">return</strong> e;
<a class="jxr_linenumber" name="910" href="#910">910</a>         }
<a class="jxr_linenumber" name="911" href="#911">911</a> 
<a class="jxr_linenumber" name="912" href="#912">912</a>         <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">void</strong> remove() {
<a class="jxr_linenumber" name="913" href="#913">913</a>             <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> p = lastRet;
<a class="jxr_linenumber" name="914" href="#914">914</a>             <strong class="jxr_keyword">if</strong> (p == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="915" href="#915">915</a>                 <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalStateException();
<a class="jxr_linenumber" name="916" href="#916">916</a>             }
<a class="jxr_linenumber" name="917" href="#917">917</a>             <strong class="jxr_keyword">if</strong> (p.tryMatchData()) {
<a class="jxr_linenumber" name="918" href="#918">918</a>                 unsplice(lastPred, p);
<a class="jxr_linenumber" name="919" href="#919">919</a>             }
<a class="jxr_linenumber" name="920" href="#920">920</a>         }
<a class="jxr_linenumber" name="921" href="#921">921</a>     }
<a class="jxr_linenumber" name="922" href="#922">922</a> 
<a class="jxr_linenumber" name="923" href="#923">923</a>     <em class="jxr_comment">/*<em class="jxr_comment"> -------------- Removal methods -------------- */</em></em>
<a class="jxr_linenumber" name="924" href="#924">924</a> 
<a class="jxr_linenumber" name="925" href="#925">925</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="926" href="#926">926</a> <em class="jxr_javadoccomment">     * Unsplices (now or later) the given deleted/cancelled node with</em>
<a class="jxr_linenumber" name="927" href="#927">927</a> <em class="jxr_javadoccomment">     * the given predecessor.</em>
<a class="jxr_linenumber" name="928" href="#928">928</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="929" href="#929">929</a> <em class="jxr_javadoccomment">     * @param pred a node that was at one time known to be the</em>
<a class="jxr_linenumber" name="930" href="#930">930</a> <em class="jxr_javadoccomment">     * predecessor of s, or null or s itself if s is/was at head</em>
<a class="jxr_linenumber" name="931" href="#931">931</a> <em class="jxr_javadoccomment">     * @param s the node to be unspliced</em>
<a class="jxr_linenumber" name="932" href="#932">932</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="933" href="#933">933</a>     <strong class="jxr_keyword">final</strong> <strong class="jxr_keyword">void</strong> unsplice(<a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> pred, <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> s) {
<a class="jxr_linenumber" name="934" href="#934">934</a>         s.forgetContents(); <em class="jxr_comment">// forget unneeded fields</em>
<a class="jxr_linenumber" name="935" href="#935">935</a>         <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="936" href="#936">936</a> <em class="jxr_comment">         * See above for rationale. Briefly: if pred still points to</em>
<a class="jxr_linenumber" name="937" href="#937">937</a> <em class="jxr_comment">         * s, try to unlink s.  If s cannot be unlinked, because it is</em>
<a class="jxr_linenumber" name="938" href="#938">938</a> <em class="jxr_comment">         * trailing node or pred might be unlinked, and neither pred</em>
<a class="jxr_linenumber" name="939" href="#939">939</a> <em class="jxr_comment">         * nor s are head or offlist, add to sweepVotes, and if enough</em>
<a class="jxr_linenumber" name="940" href="#940">940</a> <em class="jxr_comment">         * votes have accumulated, sweep.</em>
<a class="jxr_linenumber" name="941" href="#941">941</a> <em class="jxr_comment">         */</em>
<a class="jxr_linenumber" name="942" href="#942">942</a>         <strong class="jxr_keyword">if</strong> (pred != <strong class="jxr_keyword">null</strong> &amp;&amp; pred != s &amp;&amp; pred.next == s) {
<a class="jxr_linenumber" name="943" href="#943">943</a>             <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> n = s.next;
<a class="jxr_linenumber" name="944" href="#944">944</a>             <strong class="jxr_keyword">if</strong> (n == <strong class="jxr_keyword">null</strong> ||
<a class="jxr_linenumber" name="945" href="#945">945</a>                 n != s &amp;&amp; pred.casNext(s, n) &amp;&amp; pred.isMatched()) {
<a class="jxr_linenumber" name="946" href="#946">946</a>                 <strong class="jxr_keyword">for</strong> (;;) {               <em class="jxr_comment">// check if at, or could be, head</em>
<a class="jxr_linenumber" name="947" href="#947">947</a>                     <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> h = head;
<a class="jxr_linenumber" name="948" href="#948">948</a>                     <strong class="jxr_keyword">if</strong> (h == pred || h == s || h == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="949" href="#949">949</a>                         <strong class="jxr_keyword">return</strong>;          <em class="jxr_comment">// at head or list empty</em>
<a class="jxr_linenumber" name="950" href="#950">950</a>                     }
<a class="jxr_linenumber" name="951" href="#951">951</a>                     <strong class="jxr_keyword">if</strong> (!h.isMatched()) {
<a class="jxr_linenumber" name="952" href="#952">952</a>                         <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="953" href="#953">953</a>                     }
<a class="jxr_linenumber" name="954" href="#954">954</a>                     <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Node</a> hn = h.next;
<a class="jxr_linenumber" name="955" href="#955">955</a>                     <strong class="jxr_keyword">if</strong> (hn == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="956" href="#956">956</a>                         <strong class="jxr_keyword">return</strong>;          <em class="jxr_comment">// now empty</em>
<a class="jxr_linenumber" name="957" href="#957">957</a>                     }
<a class="jxr_linenumber" name="958" href="#958">958</a>                     <strong class="jxr_keyword">if</strong> (hn != h &amp;&amp; casHead(h, hn)) {
<a class="jxr_linenumber" name="959" href="#959">959</a>                         h.forgetNext();  <em class="jxr_comment">// advance head</em>
<a class="jxr_linenumber" name="960" href="#960">960</a>                     }
<a class="jxr_linenumber" name="961" href="#961">961</a>                 }
<a class="jxr_linenumber" name="962" href="#962">962</a>                 <strong class="jxr_keyword">if</strong> (pred.next != pred &amp;&amp; s.next != s) { <em class="jxr_comment">// recheck if offlist</em>
<a class="jxr_linenumber" name="963" href="#963">963</a>                     <strong class="jxr_keyword">for</strong> (;;) {           <em class="jxr_comment">// sweep now if enough votes</em>
<a class="jxr_linenumber" name="964" href="#964">964</a>                         <strong class="jxr_keyword">int</strong> v = sweepVotes;
<a class="jxr_linenumber" name="965" href="#965">965</a>                         <strong class="jxr_keyword">if</strong> (v &lt; SWEEP_THRESHOLD) {
<a class="jxr_linenumber" name="966" href="#966">966</a>                             <strong class="jxr_keyword">if</strong> (casSweepVotes(v, v + 1)) {
<a class="jxr_linenumber" name="967" href="#967">967</a>                                 <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="968" href="#968">968</a>                             }
<a class="jxr_linenumber" name="969" href="#969">969</a>                         }
<a class="jxr_linenumber" name="970" href="#970">970</a>                         <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (casSweepVotes(v, 0)) {
<a class="jxr_linenumber" name="971" href="#971">971</a>                             sweep();
<a class="jxr_linenumber" name="972" href="#972">972</a>                             <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="973" href="#973">973</a>                         }
<a class="jxr_linenumber" name="974" href="#974">974</a>                     }
<a class="jxr_linenumber" name="975" href="#975">975</a>                 }
<a class="jxr_linenumber" name="976" href="#976">976</a>             }
<a class="jxr_linenumber" name="977" href="#977">977</a>         }
<a class="jxr_linenumber" name="978" href="#978">978</a>     }
<a class="jxr_linenumber" name="979" href="#979">979</a> 
<a class="jxr_linenumber" name="980" href="#980">980</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="981" href="#981">981</a> <em class="jxr_javadoccomment">     * Unlinks matched (typically cancelled) nodes encountered in a</em>
<a class="jxr_linenumber" name="982" href="#982">982</a> <em class="jxr_javadoccomment">     * traversal from head.</em>
<a class="jxr_linenumber" name="983" href="#983">983</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="984" href="#984">984</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">void</strong> sweep() {
<a class="jxr_linenumber" name="985" href="#985">985</a>         <strong class="jxr_keyword">for</strong> (Node p = head, s, n; p != <strong class="jxr_keyword">null</strong> &amp;&amp; (s = p.next) != <strong class="jxr_keyword">null</strong>; ) {
<a class="jxr_linenumber" name="986" href="#986">986</a>             <strong class="jxr_keyword">if</strong> (!s.isMatched()) {
<a class="jxr_linenumber" name="987" href="#987">987</a>                 <em class="jxr_comment">// Unmatched nodes are never self-linked</em>
<a class="jxr_linenumber" name="988" href="#988">988</a>                 p = s;
<a class="jxr_linenumber" name="989" href="#989">989</a>             } <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> ((n = s.next) == <strong class="jxr_keyword">null</strong>) { <em class="jxr_comment">// trailing node is pinned</em>
<a class="jxr_linenumber" name="990" href="#990">990</a>                 <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="991" href="#991">991</a>             } <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (s == n) { <em class="jxr_comment">// stale</em>
<a class="jxr_linenumber" name="992" href="#992">992</a>                 <em class="jxr_comment">// No need to also check for p == s, since that implies s == n</em>
<a class="jxr_linenumber" name="993" href="#993">993</a>                 p = head;
<a class="jxr_linenumber" name="994" href="#994">994</a>             } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="995" href="#995">995</a>                 p.casNext(s, n);
<a class="jxr_linenumber" name="996" href="#996">996</a>             }
<a class="jxr_linenumber" name="997" href="#997">997</a>         }
<a class="jxr_linenumber" name="998" href="#998">998</a>     }
<a class="jxr_linenumber" name="999" href="#999">999</a> 
<a class="jxr_linenumber" name="1000" href="#1000">1000</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1001" href="#1001">1001</a> <em class="jxr_javadoccomment">     * Main implementation of remove(Object)</em>
<a class="jxr_linenumber" name="1002" href="#1002">1002</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1003" href="#1003">1003</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">boolean</strong> findAndRemove(Object e) {
<a class="jxr_linenumber" name="1004" href="#1004">1004</a>         <strong class="jxr_keyword">if</strong> (e != <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1005" href="#1005">1005</a>             <strong class="jxr_keyword">for</strong> (Node pred = <strong class="jxr_keyword">null</strong>, p = head; p != <strong class="jxr_keyword">null</strong>; ) {
<a class="jxr_linenumber" name="1006" href="#1006">1006</a>                 Object item = p.item;
<a class="jxr_linenumber" name="1007" href="#1007">1007</a>                 <strong class="jxr_keyword">if</strong> (p.isData) {
<a class="jxr_linenumber" name="1008" href="#1008">1008</a>                     <strong class="jxr_keyword">if</strong> (item != <strong class="jxr_keyword">null</strong> &amp;&amp; item != p &amp;&amp; e.equals(item) &amp;&amp;
<a class="jxr_linenumber" name="1009" href="#1009">1009</a>                         p.tryMatchData()) {
<a class="jxr_linenumber" name="1010" href="#1010">1010</a>                         unsplice(pred, p);
<a class="jxr_linenumber" name="1011" href="#1011">1011</a>                         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="1012" href="#1012">1012</a>                     }
<a class="jxr_linenumber" name="1013" href="#1013">1013</a>                 }
<a class="jxr_linenumber" name="1014" href="#1014">1014</a>                 <strong class="jxr_keyword">else</strong> <strong class="jxr_keyword">if</strong> (item == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1015" href="#1015">1015</a>                     <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="1016" href="#1016">1016</a>                 }
<a class="jxr_linenumber" name="1017" href="#1017">1017</a>                 pred = p;
<a class="jxr_linenumber" name="1018" href="#1018">1018</a>                 <strong class="jxr_keyword">if</strong> ((p = p.next) == pred) { <em class="jxr_comment">// stale</em>
<a class="jxr_linenumber" name="1019" href="#1019">1019</a>                     pred = <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="1020" href="#1020">1020</a>                     p = head;
<a class="jxr_linenumber" name="1021" href="#1021">1021</a>                 }
<a class="jxr_linenumber" name="1022" href="#1022">1022</a>             }
<a class="jxr_linenumber" name="1023" href="#1023">1023</a>         }
<a class="jxr_linenumber" name="1024" href="#1024">1024</a>         <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="1025" href="#1025">1025</a>     }
<a class="jxr_linenumber" name="1026" href="#1026">1026</a> 
<a class="jxr_linenumber" name="1027" href="#1027">1027</a> 
<a class="jxr_linenumber" name="1028" href="#1028">1028</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1029" href="#1029">1029</a> <em class="jxr_javadoccomment">     * Creates an initially empty {@code LinkedTransferQueue}.</em>
<a class="jxr_linenumber" name="1030" href="#1030">1030</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1031" href="#1031">1031</a>     <strong class="jxr_keyword">public</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">LinkedTransferQueue</a>() {
<a class="jxr_linenumber" name="1032" href="#1032">1032</a>         <strong class="jxr_keyword">super</strong>();
<a class="jxr_linenumber" name="1033" href="#1033">1033</a>     }
<a class="jxr_linenumber" name="1034" href="#1034">1034</a> 
<a class="jxr_linenumber" name="1035" href="#1035">1035</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1036" href="#1036">1036</a> <em class="jxr_javadoccomment">     * Creates a {@code LinkedTransferQueue}</em>
<a class="jxr_linenumber" name="1037" href="#1037">1037</a> <em class="jxr_javadoccomment">     * initially containing the elements of the given collection,</em>
<a class="jxr_linenumber" name="1038" href="#1038">1038</a> <em class="jxr_javadoccomment">     * added in traversal order of the collection's iterator.</em>
<a class="jxr_linenumber" name="1039" href="#1039">1039</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1040" href="#1040">1040</a> <em class="jxr_javadoccomment">     * @param c the collection of elements to initially contain</em>
<a class="jxr_linenumber" name="1041" href="#1041">1041</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified collection or any</em>
<a class="jxr_linenumber" name="1042" href="#1042">1042</a> <em class="jxr_javadoccomment">     *         of its elements are null</em>
<a class="jxr_linenumber" name="1043" href="#1043">1043</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1044" href="#1044">1044</a>     <strong class="jxr_keyword">public</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">LinkedTransferQueue</a>(Collection&lt;? <strong class="jxr_keyword">extends</strong> E&gt; c) {
<a class="jxr_linenumber" name="1045" href="#1045">1045</a>         <strong class="jxr_keyword">this</strong>();
<a class="jxr_linenumber" name="1046" href="#1046">1046</a>         addAll(c);
<a class="jxr_linenumber" name="1047" href="#1047">1047</a>     }
<a class="jxr_linenumber" name="1048" href="#1048">1048</a> 
<a class="jxr_linenumber" name="1049" href="#1049">1049</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1050" href="#1050">1050</a> <em class="jxr_javadoccomment">     * Inserts the specified element at the tail of this queue.</em>
<a class="jxr_linenumber" name="1051" href="#1051">1051</a> <em class="jxr_javadoccomment">     * As the queue is unbounded, this method will never block.</em>
<a class="jxr_linenumber" name="1052" href="#1052">1052</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1053" href="#1053">1053</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1054" href="#1054">1054</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1055" href="#1055">1055</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">void</strong> put(E e) {
<a class="jxr_linenumber" name="1056" href="#1056">1056</a>         xfer(e, <strong class="jxr_keyword">true</strong>, ASYNC, 0);
<a class="jxr_linenumber" name="1057" href="#1057">1057</a>     }
<a class="jxr_linenumber" name="1058" href="#1058">1058</a> 
<a class="jxr_linenumber" name="1059" href="#1059">1059</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1060" href="#1060">1060</a> <em class="jxr_javadoccomment">     * Inserts the specified element at the tail of this queue.</em>
<a class="jxr_linenumber" name="1061" href="#1061">1061</a> <em class="jxr_javadoccomment">     * As the queue is unbounded, this method will never block or</em>
<a class="jxr_linenumber" name="1062" href="#1062">1062</a> <em class="jxr_javadoccomment">     * return {@code false}.</em>
<a class="jxr_linenumber" name="1063" href="#1063">1063</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1064" href="#1064">1064</a> <em class="jxr_javadoccomment">     * @return {@code true} (as specified by</em>
<a class="jxr_linenumber" name="1065" href="#1065">1065</a> <em class="jxr_javadoccomment">     *  {@link BlockingQueue#offer(Object,long,TimeUnit) BlockingQueue.offer})</em>
<a class="jxr_linenumber" name="1066" href="#1066">1066</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1067" href="#1067">1067</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1068" href="#1068">1068</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> offer(E e, <strong class="jxr_keyword">long</strong> timeout, TimeUnit unit) {
<a class="jxr_linenumber" name="1069" href="#1069">1069</a>         xfer(e, <strong class="jxr_keyword">true</strong>, ASYNC, 0);
<a class="jxr_linenumber" name="1070" href="#1070">1070</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="1071" href="#1071">1071</a>     }
<a class="jxr_linenumber" name="1072" href="#1072">1072</a> 
<a class="jxr_linenumber" name="1073" href="#1073">1073</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1074" href="#1074">1074</a> <em class="jxr_javadoccomment">     * Inserts the specified element at the tail of this queue.</em>
<a class="jxr_linenumber" name="1075" href="#1075">1075</a> <em class="jxr_javadoccomment">     * As the queue is unbounded, this method will never return {@code false}.</em>
<a class="jxr_linenumber" name="1076" href="#1076">1076</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1077" href="#1077">1077</a> <em class="jxr_javadoccomment">     * @return {@code true} (as specified by</em>
<a class="jxr_linenumber" name="1078" href="#1078">1078</a> <em class="jxr_javadoccomment">     *         {@link BlockingQueue#offer(Object) BlockingQueue.offer})</em>
<a class="jxr_linenumber" name="1079" href="#1079">1079</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1080" href="#1080">1080</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1081" href="#1081">1081</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> offer(E e) {
<a class="jxr_linenumber" name="1082" href="#1082">1082</a>         xfer(e, <strong class="jxr_keyword">true</strong>, ASYNC, 0);
<a class="jxr_linenumber" name="1083" href="#1083">1083</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="1084" href="#1084">1084</a>     }
<a class="jxr_linenumber" name="1085" href="#1085">1085</a> 
<a class="jxr_linenumber" name="1086" href="#1086">1086</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1087" href="#1087">1087</a> <em class="jxr_javadoccomment">     * Inserts the specified element at the tail of this queue.</em>
<a class="jxr_linenumber" name="1088" href="#1088">1088</a> <em class="jxr_javadoccomment">     * As the queue is unbounded, this method will never throw</em>
<a class="jxr_linenumber" name="1089" href="#1089">1089</a> <em class="jxr_javadoccomment">     * {@link IllegalStateException} or return {@code false}.</em>
<a class="jxr_linenumber" name="1090" href="#1090">1090</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1091" href="#1091">1091</a> <em class="jxr_javadoccomment">     * @return {@code true} (as specified by {@link Collection#add})</em>
<a class="jxr_linenumber" name="1092" href="#1092">1092</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1093" href="#1093">1093</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1094" href="#1094">1094</a>     @Override
<a class="jxr_linenumber" name="1095" href="#1095">1095</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> add(E e) {
<a class="jxr_linenumber" name="1096" href="#1096">1096</a>         xfer(e, <strong class="jxr_keyword">true</strong>, ASYNC, 0);
<a class="jxr_linenumber" name="1097" href="#1097">1097</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="1098" href="#1098">1098</a>     }
<a class="jxr_linenumber" name="1099" href="#1099">1099</a> 
<a class="jxr_linenumber" name="1100" href="#1100">1100</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1101" href="#1101">1101</a> <em class="jxr_javadoccomment">     * Transfers the element to a waiting consumer immediately, if possible.</em>
<a class="jxr_linenumber" name="1102" href="#1102">1102</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1103" href="#1103">1103</a> <em class="jxr_javadoccomment">     * &lt;p&gt;More precisely, transfers the specified element immediately</em>
<a class="jxr_linenumber" name="1104" href="#1104">1104</a> <em class="jxr_javadoccomment">     * if there exists a consumer already waiting to receive it (in</em>
<a class="jxr_linenumber" name="1105" href="#1105">1105</a> <em class="jxr_javadoccomment">     * {@link #take} or timed {@link #poll(long,TimeUnit) poll}),</em>
<a class="jxr_linenumber" name="1106" href="#1106">1106</a> <em class="jxr_javadoccomment">     * otherwise returning {@code false} without enqueuing the element.</em>
<a class="jxr_linenumber" name="1107" href="#1107">1107</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1108" href="#1108">1108</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1109" href="#1109">1109</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1110" href="#1110">1110</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> tryTransfer(E e) {
<a class="jxr_linenumber" name="1111" href="#1111">1111</a>         <strong class="jxr_keyword">return</strong> xfer(e, <strong class="jxr_keyword">true</strong>, NOW, 0) == <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="1112" href="#1112">1112</a>     }
<a class="jxr_linenumber" name="1113" href="#1113">1113</a> 
<a class="jxr_linenumber" name="1114" href="#1114">1114</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1115" href="#1115">1115</a> <em class="jxr_javadoccomment">     * Transfers the element to a consumer, waiting if necessary to do so.</em>
<a class="jxr_linenumber" name="1116" href="#1116">1116</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1117" href="#1117">1117</a> <em class="jxr_javadoccomment">     * &lt;p&gt;More precisely, transfers the specified element immediately</em>
<a class="jxr_linenumber" name="1118" href="#1118">1118</a> <em class="jxr_javadoccomment">     * if there exists a consumer already waiting to receive it (in</em>
<a class="jxr_linenumber" name="1119" href="#1119">1119</a> <em class="jxr_javadoccomment">     * {@link #take} or timed {@link #poll(long,TimeUnit) poll}),</em>
<a class="jxr_linenumber" name="1120" href="#1120">1120</a> <em class="jxr_javadoccomment">     * else inserts the specified element at the tail of this queue</em>
<a class="jxr_linenumber" name="1121" href="#1121">1121</a> <em class="jxr_javadoccomment">     * and waits until the element is received by a consumer.</em>
<a class="jxr_linenumber" name="1122" href="#1122">1122</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1123" href="#1123">1123</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1124" href="#1124">1124</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1125" href="#1125">1125</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">void</strong> transfer(E e) <strong class="jxr_keyword">throws</strong> InterruptedException {
<a class="jxr_linenumber" name="1126" href="#1126">1126</a>         <strong class="jxr_keyword">if</strong> (xfer(e, <strong class="jxr_keyword">true</strong>, SYNC, 0) != <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1127" href="#1127">1127</a>             Thread.interrupted(); <em class="jxr_comment">// failure possible only due to interrupt</em>
<a class="jxr_linenumber" name="1128" href="#1128">1128</a>             <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> InterruptedException();
<a class="jxr_linenumber" name="1129" href="#1129">1129</a>         }
<a class="jxr_linenumber" name="1130" href="#1130">1130</a>     }
<a class="jxr_linenumber" name="1131" href="#1131">1131</a> 
<a class="jxr_linenumber" name="1132" href="#1132">1132</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1133" href="#1133">1133</a> <em class="jxr_javadoccomment">     * Transfers the element to a consumer if it is possible to do so</em>
<a class="jxr_linenumber" name="1134" href="#1134">1134</a> <em class="jxr_javadoccomment">     * before the timeout elapses.</em>
<a class="jxr_linenumber" name="1135" href="#1135">1135</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1136" href="#1136">1136</a> <em class="jxr_javadoccomment">     * &lt;p&gt;More precisely, transfers the specified element immediately</em>
<a class="jxr_linenumber" name="1137" href="#1137">1137</a> <em class="jxr_javadoccomment">     * if there exists a consumer already waiting to receive it (in</em>
<a class="jxr_linenumber" name="1138" href="#1138">1138</a> <em class="jxr_javadoccomment">     * {@link #take} or timed {@link #poll(long,TimeUnit) poll}),</em>
<a class="jxr_linenumber" name="1139" href="#1139">1139</a> <em class="jxr_javadoccomment">     * else inserts the specified element at the tail of this queue</em>
<a class="jxr_linenumber" name="1140" href="#1140">1140</a> <em class="jxr_javadoccomment">     * and waits until the element is received by a consumer,</em>
<a class="jxr_linenumber" name="1141" href="#1141">1141</a> <em class="jxr_javadoccomment">     * returning {@code false} if the specified wait time elapses</em>
<a class="jxr_linenumber" name="1142" href="#1142">1142</a> <em class="jxr_javadoccomment">     * before the element can be transferred.</em>
<a class="jxr_linenumber" name="1143" href="#1143">1143</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1144" href="#1144">1144</a> <em class="jxr_javadoccomment">     * @throws NullPointerException if the specified element is null</em>
<a class="jxr_linenumber" name="1145" href="#1145">1145</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1146" href="#1146">1146</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> tryTransfer(E e, <strong class="jxr_keyword">long</strong> timeout, TimeUnit unit)
<a class="jxr_linenumber" name="1147" href="#1147">1147</a>         <strong class="jxr_keyword">throws</strong> InterruptedException {
<a class="jxr_linenumber" name="1148" href="#1148">1148</a>         <strong class="jxr_keyword">if</strong> (xfer(e, <strong class="jxr_keyword">true</strong>, TIMED, unit.toNanos(timeout)) == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1149" href="#1149">1149</a>             <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="1150" href="#1150">1150</a>         }
<a class="jxr_linenumber" name="1151" href="#1151">1151</a>         <strong class="jxr_keyword">if</strong> (!Thread.interrupted()) {
<a class="jxr_linenumber" name="1152" href="#1152">1152</a>             <strong class="jxr_keyword">return</strong> false;
<a class="jxr_linenumber" name="1153" href="#1153">1153</a>         }
<a class="jxr_linenumber" name="1154" href="#1154">1154</a>         <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> InterruptedException();
<a class="jxr_linenumber" name="1155" href="#1155">1155</a>     }
<a class="jxr_linenumber" name="1156" href="#1156">1156</a> 
<a class="jxr_linenumber" name="1157" href="#1157">1157</a>     <strong class="jxr_keyword">public</strong> E take() <strong class="jxr_keyword">throws</strong> InterruptedException {
<a class="jxr_linenumber" name="1158" href="#1158">1158</a>         E e = xfer(<strong class="jxr_keyword">null</strong>, false, SYNC, 0);
<a class="jxr_linenumber" name="1159" href="#1159">1159</a>         <strong class="jxr_keyword">if</strong> (e != <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1160" href="#1160">1160</a>             <strong class="jxr_keyword">return</strong> e;
<a class="jxr_linenumber" name="1161" href="#1161">1161</a>         }
<a class="jxr_linenumber" name="1162" href="#1162">1162</a>         Thread.interrupted();
<a class="jxr_linenumber" name="1163" href="#1163">1163</a>         <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> InterruptedException();
<a class="jxr_linenumber" name="1164" href="#1164">1164</a>     }
<a class="jxr_linenumber" name="1165" href="#1165">1165</a> 
<a class="jxr_linenumber" name="1166" href="#1166">1166</a>     <strong class="jxr_keyword">public</strong> E poll(<strong class="jxr_keyword">long</strong> timeout, TimeUnit unit) <strong class="jxr_keyword">throws</strong> InterruptedException {
<a class="jxr_linenumber" name="1167" href="#1167">1167</a>         E e = xfer(<strong class="jxr_keyword">null</strong>, false, TIMED, unit.toNanos(timeout));
<a class="jxr_linenumber" name="1168" href="#1168">1168</a>         <strong class="jxr_keyword">if</strong> (e != <strong class="jxr_keyword">null</strong> || !Thread.interrupted()) {
<a class="jxr_linenumber" name="1169" href="#1169">1169</a>             <strong class="jxr_keyword">return</strong> e;
<a class="jxr_linenumber" name="1170" href="#1170">1170</a>         }
<a class="jxr_linenumber" name="1171" href="#1171">1171</a>         <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> InterruptedException();
<a class="jxr_linenumber" name="1172" href="#1172">1172</a>     }
<a class="jxr_linenumber" name="1173" href="#1173">1173</a> 
<a class="jxr_linenumber" name="1174" href="#1174">1174</a>     <strong class="jxr_keyword">public</strong> E poll() {
<a class="jxr_linenumber" name="1175" href="#1175">1175</a>         <strong class="jxr_keyword">return</strong> xfer(<strong class="jxr_keyword">null</strong>, false, NOW, 0);
<a class="jxr_linenumber" name="1176" href="#1176">1176</a>     }
<a class="jxr_linenumber" name="1177" href="#1177">1177</a> 
<a class="jxr_linenumber" name="1178" href="#1178">1178</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1179" href="#1179">1179</a> <em class="jxr_javadoccomment">     * @throws NullPointerException     {@inheritDoc}</em>
<a class="jxr_linenumber" name="1180" href="#1180">1180</a> <em class="jxr_javadoccomment">     * @throws IllegalArgumentException {@inheritDoc}</em>
<a class="jxr_linenumber" name="1181" href="#1181">1181</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1182" href="#1182">1182</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> drainTo(Collection&lt;? <strong class="jxr_keyword">super</strong> E&gt; c) {
<a class="jxr_linenumber" name="1183" href="#1183">1183</a>         <strong class="jxr_keyword">if</strong> (c == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1184" href="#1184">1184</a>             <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> NullPointerException();
<a class="jxr_linenumber" name="1185" href="#1185">1185</a>         }
<a class="jxr_linenumber" name="1186" href="#1186">1186</a>         <strong class="jxr_keyword">if</strong> (c == <strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="1187" href="#1187">1187</a>             <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException();
<a class="jxr_linenumber" name="1188" href="#1188">1188</a>         }
<a class="jxr_linenumber" name="1189" href="#1189">1189</a>         <strong class="jxr_keyword">int</strong> n = 0;
<a class="jxr_linenumber" name="1190" href="#1190">1190</a>         E e;
<a class="jxr_linenumber" name="1191" href="#1191">1191</a>         <strong class="jxr_keyword">while</strong> ( (e = poll()) != <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1192" href="#1192">1192</a>             c.add(e);
<a class="jxr_linenumber" name="1193" href="#1193">1193</a>             ++n;
<a class="jxr_linenumber" name="1194" href="#1194">1194</a>         }
<a class="jxr_linenumber" name="1195" href="#1195">1195</a>         <strong class="jxr_keyword">return</strong> n;
<a class="jxr_linenumber" name="1196" href="#1196">1196</a>     }
<a class="jxr_linenumber" name="1197" href="#1197">1197</a> 
<a class="jxr_linenumber" name="1198" href="#1198">1198</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1199" href="#1199">1199</a> <em class="jxr_javadoccomment">     * @throws NullPointerException     {@inheritDoc}</em>
<a class="jxr_linenumber" name="1200" href="#1200">1200</a> <em class="jxr_javadoccomment">     * @throws IllegalArgumentException {@inheritDoc}</em>
<a class="jxr_linenumber" name="1201" href="#1201">1201</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1202" href="#1202">1202</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> drainTo(Collection&lt;? <strong class="jxr_keyword">super</strong> E&gt; c, <strong class="jxr_keyword">int</strong> maxElements) {
<a class="jxr_linenumber" name="1203" href="#1203">1203</a>         <strong class="jxr_keyword">if</strong> (c == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1204" href="#1204">1204</a>             <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> NullPointerException();
<a class="jxr_linenumber" name="1205" href="#1205">1205</a>         }
<a class="jxr_linenumber" name="1206" href="#1206">1206</a>         <strong class="jxr_keyword">if</strong> (c == <strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="1207" href="#1207">1207</a>             <strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException();
<a class="jxr_linenumber" name="1208" href="#1208">1208</a>         }
<a class="jxr_linenumber" name="1209" href="#1209">1209</a>         <strong class="jxr_keyword">int</strong> n = 0;
<a class="jxr_linenumber" name="1210" href="#1210">1210</a>         E e;
<a class="jxr_linenumber" name="1211" href="#1211">1211</a>         <strong class="jxr_keyword">while</strong> (n &lt; maxElements &amp;&amp; (e = poll()) != <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1212" href="#1212">1212</a>             c.add(e);
<a class="jxr_linenumber" name="1213" href="#1213">1213</a>             ++n;
<a class="jxr_linenumber" name="1214" href="#1214">1214</a>         }
<a class="jxr_linenumber" name="1215" href="#1215">1215</a>         <strong class="jxr_keyword">return</strong> n;
<a class="jxr_linenumber" name="1216" href="#1216">1216</a>     }
<a class="jxr_linenumber" name="1217" href="#1217">1217</a> 
<a class="jxr_linenumber" name="1218" href="#1218">1218</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1219" href="#1219">1219</a> <em class="jxr_javadoccomment">     * Returns an iterator over the elements in this queue in proper</em>
<a class="jxr_linenumber" name="1220" href="#1220">1220</a> <em class="jxr_javadoccomment">     * sequence, from head to tail.</em>
<a class="jxr_linenumber" name="1221" href="#1221">1221</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1222" href="#1222">1222</a> <em class="jxr_javadoccomment">     * &lt;p&gt;The returned iterator is a "weakly consistent" iterator that</em>
<a class="jxr_linenumber" name="1223" href="#1223">1223</a> <em class="jxr_javadoccomment">     * will never throw</em>
<a class="jxr_linenumber" name="1224" href="#1224">1224</a> <em class="jxr_javadoccomment">     * {@link ConcurrentModificationException ConcurrentModificationException},</em>
<a class="jxr_linenumber" name="1225" href="#1225">1225</a> <em class="jxr_javadoccomment">     * and guarantees to traverse elements as they existed upon</em>
<a class="jxr_linenumber" name="1226" href="#1226">1226</a> <em class="jxr_javadoccomment">     * construction of the iterator, and may (but is not guaranteed</em>
<a class="jxr_linenumber" name="1227" href="#1227">1227</a> <em class="jxr_javadoccomment">     * to) reflect any modifications subsequent to construction.</em>
<a class="jxr_linenumber" name="1228" href="#1228">1228</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1229" href="#1229">1229</a> <em class="jxr_javadoccomment">     * @return an iterator over the elements in this queue in proper sequence</em>
<a class="jxr_linenumber" name="1230" href="#1230">1230</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1231" href="#1231">1231</a>     @Override
<a class="jxr_linenumber" name="1232" href="#1232">1232</a>     <strong class="jxr_keyword">public</strong> Iterator&lt;E&gt; iterator() {
<a class="jxr_linenumber" name="1233" href="#1233">1233</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">new</strong> <a href="../../../../../org/jboss/netty/util/internal/LinkedTransferQueue.html">Itr</a>();
<a class="jxr_linenumber" name="1234" href="#1234">1234</a>     }
<a class="jxr_linenumber" name="1235" href="#1235">1235</a> 
<a class="jxr_linenumber" name="1236" href="#1236">1236</a>     <strong class="jxr_keyword">public</strong> E peek() {
<a class="jxr_linenumber" name="1237" href="#1237">1237</a>         <strong class="jxr_keyword">return</strong> firstDataItem();
<a class="jxr_linenumber" name="1238" href="#1238">1238</a>     }
<a class="jxr_linenumber" name="1239" href="#1239">1239</a> 
<a class="jxr_linenumber" name="1240" href="#1240">1240</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1241" href="#1241">1241</a> <em class="jxr_javadoccomment">     * Returns {@code true} if this queue contains no elements.</em>
<a class="jxr_linenumber" name="1242" href="#1242">1242</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1243" href="#1243">1243</a> <em class="jxr_javadoccomment">     * @return {@code true} if this queue contains no elements</em>
<a class="jxr_linenumber" name="1244" href="#1244">1244</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1245" href="#1245">1245</a>     @Override
<a class="jxr_linenumber" name="1246" href="#1246">1246</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> isEmpty() {
<a class="jxr_linenumber" name="1247" href="#1247">1247</a>         <strong class="jxr_keyword">for</strong> (Node p = head; p != <strong class="jxr_keyword">null</strong>; p = succ(p)) {
<a class="jxr_linenumber" name="1248" href="#1248">1248</a>             <strong class="jxr_keyword">if</strong> (!p.isMatched()) {
<a class="jxr_linenumber" name="1249" href="#1249">1249</a>                 <strong class="jxr_keyword">return</strong> !p.isData;
<a class="jxr_linenumber" name="1250" href="#1250">1250</a>             }
<a class="jxr_linenumber" name="1251" href="#1251">1251</a>         }
<a class="jxr_linenumber" name="1252" href="#1252">1252</a>         <strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">true</strong>;
<a class="jxr_linenumber" name="1253" href="#1253">1253</a>     }
<a class="jxr_linenumber" name="1254" href="#1254">1254</a> 
<a class="jxr_linenumber" name="1255" href="#1255">1255</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> hasWaitingConsumer() {
<a class="jxr_linenumber" name="1256" href="#1256">1256</a>         <strong class="jxr_keyword">return</strong> firstOfMode(false) != <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="1257" href="#1257">1257</a>     }
<a class="jxr_linenumber" name="1258" href="#1258">1258</a> 
<a class="jxr_linenumber" name="1259" href="#1259">1259</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1260" href="#1260">1260</a> <em class="jxr_javadoccomment">     * Returns the number of elements in this queue.  If this queue</em>
<a class="jxr_linenumber" name="1261" href="#1261">1261</a> <em class="jxr_javadoccomment">     * contains more than {@code Integer.MAX_VALUE} elements, returns</em>
<a class="jxr_linenumber" name="1262" href="#1262">1262</a> <em class="jxr_javadoccomment">     * {@code Integer.MAX_VALUE}.</em>
<a class="jxr_linenumber" name="1263" href="#1263">1263</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1264" href="#1264">1264</a> <em class="jxr_javadoccomment">     * &lt;p&gt;Beware that, unlike in most collections, this method is</em>
<a class="jxr_linenumber" name="1265" href="#1265">1265</a> <em class="jxr_javadoccomment">     * &lt;em&gt;NOT&lt;/em&gt; a constant-time operation. Because of the</em>
<a class="jxr_linenumber" name="1266" href="#1266">1266</a> <em class="jxr_javadoccomment">     * asynchronous nature of these queues, determining the current</em>
<a class="jxr_linenumber" name="1267" href="#1267">1267</a> <em class="jxr_javadoccomment">     * number of elements requires an O(n) traversal.</em>
<a class="jxr_linenumber" name="1268" href="#1268">1268</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1269" href="#1269">1269</a> <em class="jxr_javadoccomment">     * @return the number of elements in this queue</em>
<a class="jxr_linenumber" name="1270" href="#1270">1270</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1271" href="#1271">1271</a>     @Override
<a class="jxr_linenumber" name="1272" href="#1272">1272</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> size() {
<a class="jxr_linenumber" name="1273" href="#1273">1273</a>         <strong class="jxr_keyword">return</strong> countOfMode(<strong class="jxr_keyword">true</strong>);
<a class="jxr_linenumber" name="1274" href="#1274">1274</a>     }
<a class="jxr_linenumber" name="1275" href="#1275">1275</a> 
<a class="jxr_linenumber" name="1276" href="#1276">1276</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> getWaitingConsumerCount() {
<a class="jxr_linenumber" name="1277" href="#1277">1277</a>         <strong class="jxr_keyword">return</strong> countOfMode(false);
<a class="jxr_linenumber" name="1278" href="#1278">1278</a>     }
<a class="jxr_linenumber" name="1279" href="#1279">1279</a> 
<a class="jxr_linenumber" name="1280" href="#1280">1280</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1281" href="#1281">1281</a> <em class="jxr_javadoccomment">     * Removes a single instance of the specified element from this queue,</em>
<a class="jxr_linenumber" name="1282" href="#1282">1282</a> <em class="jxr_javadoccomment">     * if it is present.  More formally, removes an element {@code e} such</em>
<a class="jxr_linenumber" name="1283" href="#1283">1283</a> <em class="jxr_javadoccomment">     * that {@code o.equals(e)}, if this queue contains one or more such</em>
<a class="jxr_linenumber" name="1284" href="#1284">1284</a> <em class="jxr_javadoccomment">     * elements.</em>
<a class="jxr_linenumber" name="1285" href="#1285">1285</a> <em class="jxr_javadoccomment">     * Returns {@code true} if this queue contained the specified element</em>
<a class="jxr_linenumber" name="1286" href="#1286">1286</a> <em class="jxr_javadoccomment">     * (or equivalently, if this queue changed as a result of the call).</em>
<a class="jxr_linenumber" name="1287" href="#1287">1287</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1288" href="#1288">1288</a> <em class="jxr_javadoccomment">     * @param o element to be removed from this queue, if present</em>
<a class="jxr_linenumber" name="1289" href="#1289">1289</a> <em class="jxr_javadoccomment">     * @return {@code true} if this queue changed as a result of the call</em>
<a class="jxr_linenumber" name="1290" href="#1290">1290</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1291" href="#1291">1291</a>     @Override
<a class="jxr_linenumber" name="1292" href="#1292">1292</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> remove(Object o) {
<a class="jxr_linenumber" name="1293" href="#1293">1293</a>         <strong class="jxr_keyword">return</strong> findAndRemove(o);
<a class="jxr_linenumber" name="1294" href="#1294">1294</a>     }
<a class="jxr_linenumber" name="1295" href="#1295">1295</a> 
<a class="jxr_linenumber" name="1296" href="#1296">1296</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1297" href="#1297">1297</a> <em class="jxr_javadoccomment">     * Always returns {@code Integer.MAX_VALUE} because a</em>
<a class="jxr_linenumber" name="1298" href="#1298">1298</a> <em class="jxr_javadoccomment">     * {@code LinkedTransferQueue} is not capacity constrained.</em>
<a class="jxr_linenumber" name="1299" href="#1299">1299</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1300" href="#1300">1300</a> <em class="jxr_javadoccomment">     * @return {@code Integer.MAX_VALUE} (as specified by</em>
<a class="jxr_linenumber" name="1301" href="#1301">1301</a> <em class="jxr_javadoccomment">     *         {@link BlockingQueue#remainingCapacity()})</em>
<a class="jxr_linenumber" name="1302" href="#1302">1302</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1303" href="#1303">1303</a>     <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">int</strong> remainingCapacity() {
<a class="jxr_linenumber" name="1304" href="#1304">1304</a>         <strong class="jxr_keyword">return</strong> Integer.MAX_VALUE;
<a class="jxr_linenumber" name="1305" href="#1305">1305</a>     }
<a class="jxr_linenumber" name="1306" href="#1306">1306</a> 
<a class="jxr_linenumber" name="1307" href="#1307">1307</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1308" href="#1308">1308</a> <em class="jxr_javadoccomment">     * Saves the state to a stream (that is, serializes it).</em>
<a class="jxr_linenumber" name="1309" href="#1309">1309</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1310" href="#1310">1310</a> <em class="jxr_javadoccomment">     * @serialData All of the elements (each an {@code E}) in</em>
<a class="jxr_linenumber" name="1311" href="#1311">1311</a> <em class="jxr_javadoccomment">     * the proper order, followed by a null</em>
<a class="jxr_linenumber" name="1312" href="#1312">1312</a> <em class="jxr_javadoccomment">     * @param s the stream</em>
<a class="jxr_linenumber" name="1313" href="#1313">1313</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1314" href="#1314">1314</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">void</strong> writeObject(java.io.ObjectOutputStream s)
<a class="jxr_linenumber" name="1315" href="#1315">1315</a>         <strong class="jxr_keyword">throws</strong> java.io.IOException {
<a class="jxr_linenumber" name="1316" href="#1316">1316</a>         s.defaultWriteObject();
<a class="jxr_linenumber" name="1317" href="#1317">1317</a>         <strong class="jxr_keyword">for</strong> (E e : <strong class="jxr_keyword">this</strong>) {
<a class="jxr_linenumber" name="1318" href="#1318">1318</a>             s.writeObject(e);
<a class="jxr_linenumber" name="1319" href="#1319">1319</a>         }
<a class="jxr_linenumber" name="1320" href="#1320">1320</a>         <em class="jxr_comment">// Use trailing null as sentinel</em>
<a class="jxr_linenumber" name="1321" href="#1321">1321</a>         s.writeObject(<strong class="jxr_keyword">null</strong>);
<a class="jxr_linenumber" name="1322" href="#1322">1322</a>     }
<a class="jxr_linenumber" name="1323" href="#1323">1323</a> 
<a class="jxr_linenumber" name="1324" href="#1324">1324</a>     <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="1325" href="#1325">1325</a> <em class="jxr_javadoccomment">     * Reconstitutes the Queue instance from a stream (that is,</em>
<a class="jxr_linenumber" name="1326" href="#1326">1326</a> <em class="jxr_javadoccomment">     * deserializes it).</em>
<a class="jxr_linenumber" name="1327" href="#1327">1327</a> <em class="jxr_javadoccomment">     *</em>
<a class="jxr_linenumber" name="1328" href="#1328">1328</a> <em class="jxr_javadoccomment">     * @param s the stream</em>
<a class="jxr_linenumber" name="1329" href="#1329">1329</a> <em class="jxr_javadoccomment">     */</em>
<a class="jxr_linenumber" name="1330" href="#1330">1330</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">void</strong> readObject(java.io.ObjectInputStream s)
<a class="jxr_linenumber" name="1331" href="#1331">1331</a>         <strong class="jxr_keyword">throws</strong> java.io.IOException, ClassNotFoundException {
<a class="jxr_linenumber" name="1332" href="#1332">1332</a>         s.defaultReadObject();
<a class="jxr_linenumber" name="1333" href="#1333">1333</a>         <strong class="jxr_keyword">for</strong> (;;) {
<a class="jxr_linenumber" name="1334" href="#1334">1334</a>             @SuppressWarnings(<span class="jxr_string">"unchecked"</span>) E item = (E) s.readObject();
<a class="jxr_linenumber" name="1335" href="#1335">1335</a>             <strong class="jxr_keyword">if</strong> (item == <strong class="jxr_keyword">null</strong>) {
<a class="jxr_linenumber" name="1336" href="#1336">1336</a>                 <strong class="jxr_keyword">break</strong>;
<a class="jxr_linenumber" name="1337" href="#1337">1337</a>             } <strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="1338" href="#1338">1338</a>                 offer(item);
<a class="jxr_linenumber" name="1339" href="#1339">1339</a>             }
<a class="jxr_linenumber" name="1340" href="#1340">1340</a>         }
<a class="jxr_linenumber" name="1341" href="#1341">1341</a>     }
<a class="jxr_linenumber" name="1342" href="#1342">1342</a> 
<a class="jxr_linenumber" name="1343" href="#1343">1343</a>     @SuppressWarnings(<span class="jxr_string">"rawtypes"</span>)
<a class="jxr_linenumber" name="1344" href="#1344">1344</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> AtomicReferenceFieldUpdater&lt;LinkedTransferQueue, Node&gt; headUpdater =
<a class="jxr_linenumber" name="1345" href="#1345">1345</a>         AtomicFieldUpdaterUtil.newRefUpdater(LinkedTransferQueue.<strong class="jxr_keyword">class</strong>, Node.<strong class="jxr_keyword">class</strong>, <span class="jxr_string">"head"</span>);
<a class="jxr_linenumber" name="1346" href="#1346">1346</a>     @SuppressWarnings(<span class="jxr_string">"rawtypes"</span>)
<a class="jxr_linenumber" name="1347" href="#1347">1347</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> AtomicReferenceFieldUpdater&lt;LinkedTransferQueue, Node&gt; tailUpdater =
<a class="jxr_linenumber" name="1348" href="#1348">1348</a>         AtomicFieldUpdaterUtil.newRefUpdater(LinkedTransferQueue.<strong class="jxr_keyword">class</strong>, Node.<strong class="jxr_keyword">class</strong>, <span class="jxr_string">"tail"</span>);
<a class="jxr_linenumber" name="1349" href="#1349">1349</a>     @SuppressWarnings(<span class="jxr_string">"rawtypes"</span>)
<a class="jxr_linenumber" name="1350" href="#1350">1350</a>     <strong class="jxr_keyword">private</strong> <strong class="jxr_keyword">static</strong> <strong class="jxr_keyword">final</strong> AtomicIntegerFieldUpdater&lt;LinkedTransferQueue&gt; sweepVotesUpdater =
<a class="jxr_linenumber" name="1351" href="#1351">1351</a>         AtomicFieldUpdaterUtil.newIntUpdater(LinkedTransferQueue.<strong class="jxr_keyword">class</strong>, <span class="jxr_string">"sweepVotes"</span>);
<a class="jxr_linenumber" name="1352" href="#1352">1352</a> }
<a class="jxr_linenumber" name="1353" href="#1353">1353</a> 
</pre>
<hr/><div id="footer">This page was automatically generated by <a href="http://maven.apache.org/">Maven</a></div></body>
</html>

